Rollback r18274 as its legal to have a sequence number smaller than the

expected one. It doesn't necessarily means the message is duplicated,
it can simply signify the message is out of sequence and the counter
overflowed.

This commit was SVN r18323.

The following SVN revision numbers were found above:
  r18274 --> open-mpi/ompi@73c9de3af9

ompi/mca/pml/ob1/pml_ob1_recvfrag.c

@@ -298,17 +298,8 @@ static mca_pml_ob1_recv_frag_t *check_cantmatch_for_match(
         /*
          * If the message has the next expected seq from that proc...
          */
-        if(hdr->hdr_seq != proc->expected_sequence) {
-            if( hdr->hdr_seq < proc->expected_sequence ) {
-                opal_output( 0, "Unbelievable situation ... we got a duplicated fragment "
-                             "with seq number of %d (expected %d) from %s\n",
-                             (int)hdr->hdr_seq, (int)proc->expected_sequence,
-                             proc->ompi_proc->proc_hostname );
-                opal_list_remove_item(&proc->frags_cant_match, (opal_list_item_t*)frag);
-                MCA_PML_OB1_RECV_FRAG_RETURN(frag);  /* Drop it !!! */
-            }
+        if(hdr->hdr_seq != proc->expected_sequence)
             continue;
-        }
 
         opal_list_remove_item(&proc->frags_cant_match, (opal_list_item_t*)frag);
         return frag;