Fix a segfault that turned up in more MPI_THREAD_MULTIPLE testing.

Same sort of problem and fix as described in r12323 - mca_pml_ob1_recv_frag_progress() was segfaulting due to a NULL req_proc pointer.  The path leading to this was through the mca_pml_ob1_check_cantmatch_for_match() function, where we can match a frag using the same macros as mca_pml_ob1_frag_match() and never initialize the req_proc pointer.

This commit was SVN r12582.

The following SVN revision numbers were found above:
  r12323 --> open-mpi/ompi@c752502dee

ompi/mca/pml/ob1/pml_ob1_recvfrag.c

@@ -737,6 +737,7 @@ rematch:
 
                 /* if match found, process data */
                 if (match) {
+                    match->req_recv.req_base.req_proc = proc->ompi_proc;
 
                     /*
                      * If this was a probe need to queue fragment on unexpected list