If a BTL isn't needed due to exclusivity ranking, need to call a matching

inuse decrement for the increment that was at the start of the procs loop.
Otherwise, the inuse count can end up higher than it actually is and a btl
can end up in the progress loop when it isn't active to any peer.

Refs trac:543

This commit was SVN r12938.

The following Trac tickets were found above:
  Ticket 543 --> https://svn.open-mpi.org/trac/ompi/ticket/543

ompi/mca/bml/r2/bml_r2.c

@@ -284,6 +284,7 @@ int mca_bml_r2_add_procs(
                         if(btl_endpoints[p] != NULL) {
                             btl->btl_del_procs(btl, 1, &proc, &btl_endpoints[p]);
                         }
+                        btl_inuse--;
                         continue;
                     }
                 }