COLL/FCA: revert to prev barrier if called from finalize

FCA barrier may not complete if FCA progress is not called periodically.
PMI/PMI2 API that can be used in rte barrier has no provision for calling
external progress function.

So it is possible that during finalize some ranks will be stuck
in fca barrier while others are in PMI barrier.

ompi/mca/coll/fca/coll_fca_ops.c

@@ -153,6 +153,10 @@ int mca_coll_fca_barrier(struct ompi_communicator_t *comm,
     int ret;
 
     FCA_VERBOSE(5,"Using FCA Barrier");
+    if (OPAL_UNLIKELY(ompi_mpi_finalize_started)) {
+        FCA_VERBOSE(5, "In finalize, reverting to previous barrier");
+        goto orig_barrier;
+    }
     ret = fca_do_barrier(fca_module->fca_comm);
     if (ret < 0) {
         if (ret == -EUSEMPI) {