Remove trylock + unlock in acl_reset_condvar()

[IlanTruanovsky]

See #276 for an explanation on why this needs to be done.

In short, assuming library destructors work as we expect (i.e. they do not get called on abort), this code is unnecessary and can introduce undefined behavior.

This will also fix the following Coverity issues:

lib/acl_threadsupport/test/acl_threadsupport_test.cpp:333:3:
  Type: Double unlock (LOCK)

lib/acl_threadsupport/test/acl_threadsupport_test.cpp:332:3:
  1. unlock: "acl_release_condvar" unlocks "cc.waiter_mutex".
lib/acl_threadsupport/src/acl_threadsupport.c:375:5:
  1.1. unlock: "pthread_mutex_unlock" unlocks "C->waiter_mutex".
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:333:3:
  2. double_unlock: "acl_reset_condvar" unlocks "cc.waiter_mutex" while it is unlocked.
lib/acl_threadsupport/src/acl_threadsupport.c:300:5:
  2.1. unlock: "pthread_mutex_unlock" unlocks "C->waiter_mutex".
lib/acl_threadsupport/src/acl_threadsupport.c:301:5:
  2.2. destroy: "pthread_mutex_destroy" destroys "C->waiter_mutex".

lib/acl_threadsupport/test/acl_threadsupport_test.cpp:353:3:
  Type: Double unlock (LOCK)

lib/acl_threadsupport/test/acl_threadsupport_test.cpp:345:3:
  1. path: Condition "i < 10000000U /* COUNT */", taking true branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:346:5:
  2. path: Condition "0 == i % (1000000U /* COUNT / 10 */)", taking true branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:352:3:
  3. path: Jumping back to the beginning of the loop.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:345:3:
  4. path: Condition "i < 10000000U /* COUNT */", taking true branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:346:5:
  5. path: Condition "0 == i % (1000000U /* COUNT / 10 */)", taking false branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:351:5:
  6. unlock: "acl_release_condvar" unlocks "cc.waiter_mutex".
lib/acl_threadsupport/src/acl_threadsupport.c:375:5:
  6.1. unlock: "pthread_mutex_unlock" unlocks "C->waiter_mutex".
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:352:3:
  7. path: Jumping back to the beginning of the loop.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:345:3:
  8. path: Condition "i < 10000000U /* COUNT */", taking false branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:353:3:
  9. double_unlock: "acl_reset_condvar" unlocks "cc.waiter_mutex" while it is unlocked.
lib/acl_threadsupport/src/acl_threadsupport.c:300:5:
  9.1. unlock: "pthread_mutex_unlock" unlocks "C->waiter_mutex".
lib/acl_threadsupport/src/acl_threadsupport.c:301:5:
  9.2. destroy: "pthread_mutex_destroy" destroys "C->waiter_mutex".

lib/acl_threadsupport/test/acl_threadsupport_test.cpp:477:3:
  Type: Double unlock (LOCK)

lib/acl_threadsupport/test/acl_threadsupport_test.cpp:464:3:
  1. path: Condition "1 != acl_timed_wait_condvar(&cc, 1)", taking false branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:465:3:
  2. path: Condition "1 != cc.timedout[0]", taking true branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:465:3:
  3. path: Falling through to end of if statement.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:473:3:
  4. path: Condition "0 != acl_timed_wait_condvar(&cc, 1)", taking true branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:473:3:
  5. path: Falling through to end of if statement.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:474:3:
  6. path: Condition "0 != cc.timedout[1]", taking true branch.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:474:3:
  7. path: Falling through to end of if statement.
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:475:3:
  8. unlock: "acl_release_condvar" unlocks "cc.waiter_mutex".
lib/acl_threadsupport/src/acl_threadsupport.c:375:5:
  8.1. unlock: "pthread_mutex_unlock" unlocks "C->waiter_mutex".
lib/acl_threadsupport/test/acl_threadsupport_test.cpp:477:3:
  9. double_unlock: "acl_reset_condvar" unlocks "cc.waiter_mutex" while it is unlocked.
lib/acl_threadsupport/src/acl_threadsupport.c:300:5:
  9.1. unlock: "pthread_mutex_unlock" unlocks "C->waiter_mutex".
lib/acl_threadsupport/src/acl_threadsupport.c:301:5:
  9.2. destroy: "pthread_mutex_destroy" destroys "C->waiter_mutex".

[pcolberg]

Thanks @IlanTruanovsky for your detailed exploration! I will wait with the merge until integration passes.