Make write verification work even without read test

[jyvet]

Context: IOR outputs errors when the '-w -W' flags are used
without '-r'. Write a file using with check write option
should be possible even without setting read.

This patch fixes a condition which was introduced for
HDFS to remove RDWR flag in some particular cases.
Write check was set with the write only flag but it
requieres the read flag.

[glennklockwood]

Can you provide an example input that triggers the bug that this is fixing? I am not getting errors when I naively try to reproduce the issue:

$ ./test/_inst/bin/ior -w -W
IOR-3.2.0: MPI Coordinated Test of Parallel I/O
Began               : Fri Sep 21 18:05:40 2018
Command line        : ./test/_inst/bin/ior -w -W
Machine             : Darwin ...
TestID              : 0
StartTime           : Fri Sep 21 18:05:40 2018
Path                : ...
FS                  : 931.5 GiB   Used FS: 14.4%   Inodes: 8796093022208.0 Mi   Used Inodes: 0.0%

Options: 
api                 : POSIX
apiVersion          : 
test filename       : testFile
access              : single-shared-file
type                : independent
segments            : 1
ordering in a file  : sequential
ordering inter file : no tasks offsets
tasks               : 1
clients per node    : 1
repetitions         : 1
xfersize            : 262144 bytes
blocksize           : 1 MiB
aggregate filesize  : 1 MiB

Results: 

access    bw(MiB/s)  block(KiB) xfer(KiB)  open(s)    wr/rd(s)   close(s)   total(s)   iter
------    ---------  ---------- ---------  --------   --------   --------   --------   ----
write     2457.12    1024.00    256.00     0.000059   0.000255   0.000093   0.000407   0   
remove    -          -          -          -          -          -          0.000127   0   
Max Write: 2457.12 MiB/sec (2576.48 MB/sec)

Summary of all tests:
Operation   Max(MiB)   Min(MiB)  Mean(MiB)     StdDev   Max(OPs)   Min(OPs)  Mean(OPs)     StdDev    Mean(s) Test# #Tasks tPN reps fPP reord reordoff reordrand seed segcnt   blksiz    xsize aggs(MiB)   API RefNum
write        2457.12    2457.12    2457.12       0.00    9828.48    9828.48    9828.48       0.00    0.00041     0      1   1    1   0     0        1         0    0      1  1048576   262144       1.0 POSIX      0
Finished            : Fri Sep 21 18:05:40 2018

Granted, there's no obvious sign that the write check actually worked.

[jyvet]

ah yeah sorry I should have provided more info (I thought the issue was for all backends). At least for POSIX, the open flag seems to be applied less striclty. With MPIIO (and IME) backends we get this:

./ior -vvv -a MPIIO -W -w -s 10 -t 1M -b 1M 
...
access    bw(MiB/s)  block(KiB) xfer(KiB)  open(s)    wr/rd(s)   close(s)   total(s)   iter
------    ---------  ---------- ---------  --------   --------   --------   --------   ----
Commencing write performance test: Sat Sep 22 15:04:38 2018
write     401.18     1024.00    1024.00    0.011977   0.010356   0.002564   0.024927   0   
Verifying contents of the file(s) just written.
Sat Sep 22 15:04:38 2018

ior ERROR: cannot access explicit, noncollective, MPI Access denied to file, error stack:
MPI_FILE_READ_AT(118): Cannot read from a file opened with amode MPI_MODE_WRONLY, (aiori-MPIIO.c:371)
[unset]: aborting job:
application called MPI_Abort(MPI_COMM_WORLD, -1) - process 0

But, no error is displayed if the -r flag is used

./ior -vvv -a MPIIO -W -w -r -s 10 -t 1M -b 1M 
...
access    bw(MiB/s)  block(KiB) xfer(KiB)  open(s)    wr/rd(s)   close(s)   total(s)   iter
------    ---------  ---------- ---------  --------   --------   --------   --------   ----
Commencing write performance test: Sat Sep 22 15:06:14 2018
write     711.04     1024.00    1024.00    0.001194   0.010319   0.002521   0.014064   0   
Verifying contents of the file(s) just written.
Sat Sep 22 15:06:14 2018

Commencing read performance test: Sat Sep 22 15:06:14 2018
read      874.03     1024.00    1024.00    0.000303   0.010546   0.000562   0.011441   0   
remove    -          -          -          -          -          -          0.000502   0   
Max Write: 711.04 MiB/sec (745.58 MB/sec)
Max Read:  874.03 MiB/sec (916.49 MB/sec)

with this patch:

./ior -vvv -a MPIIO -W -w  -s 10 -t 1M -b 1M 
...
access    bw(MiB/s)  block(KiB) xfer(KiB)  open(s)    wr/rd(s)   close(s)   total(s)   iter
------    ---------  ---------- ---------  --------   --------   --------   --------   ----
Commencing write performance test: Sat Sep 22 15:08:05 2018
write     681.58     1024.00    1024.00    0.001836   0.010288   0.002518   0.014672   0   
Verifying contents of the file(s) just written.
Sat Sep 22 15:08:05 2018

remove    -          -          -          -          -          -          0.000662   0   
Max Write: 681.58 MiB/sec (714.69 MB/sec)

Summary of all tests:
Operation   Max(MiB)   Min(MiB)  Mean(MiB)     StdDev   Max(OPs)   Min(OPs)  Mean(OPs)     StdDev    Mean(s) Test# #Tasks tPN reps fPP reord reordoff reordrand seed segcnt   blksiz    xsize aggs(MiB)   API RefNum
write         681.58     681.58     681.58       0.00     681.58     681.58     681.58       0.00    0.01467     0      1   1    1   0     0        1         0    0     10  1048576  1048576      10.0 MPIIO      0
Finished            : Sat Sep 22 15:08:05 2018