Make a better test for listlibs

[alcuadrado]

Our current test doesn't work. We are testing which processes have libc loaded, and that's almost all of them. We should create a dummy library that only a process known by us loads.

I think the current tests isn't spotting a bug on linux.

[alcuadrado]

I deleted the tests from listlib module as they were not doing any significant checking.

I tested OS X and Linux implementations manually, but this is not the best way to do it. We should consider doing what I mentioned when I created this issue.