Remove hack from dotest.py to fix extra output on -P command, and fix MacOSX multi-threaded test run collisions on crashlog.dylib.

On MacOSX, we need to adjust the way we clean up the crashlog dylib in deleteCrashInfoDylib().
Right now it is only geared to run one test at a time.  For now I'm just skipping the delete.
I'll work with Apple on a fix that handles this.  It seems to only cause one dylib total to
hang around that might otherwise have been deleted.  Fixes MacOSX multiple tests running
at the same time.  (I didn't hit this on Yosemite, might be an issue that only shows up
on Mavericks?)