This commit fixes a race that can occur when two threads are in the
ugni progress function at the same time. This race occurs when one
thread calls GNI_PostDataProbeById then goes to sleep then another
thread calls GNI_PostDataProbeById then GNI_EpPostDataWaitById before
the other thread wakes up. If this happens the first thread will print
a warning on GNI_EpPostDataWaitById about no matching post.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>