This commit fixes a hang reported by @nysal which happens when a
request is completed after a sync object is created but before the
sync object can be assigned to the request. In this case we need to
set the sync signaling field to false to ensure WAIT_SYNC_RELEASE does
not hang.
Fixesopen-mpi/ompi#1828
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>