pmix: Increment the reference count in PMIx_Init

The reference counting was broken which led PMIx_Finalize
to release resources early. This fixes the "use after free" scenarios
that I encountered.

(based on commit openpmix/openpmix@abfaa4c)

Author: nysal

opal/mca/pmix/pmix112/pmix/src/client/pmix_client.c

@@ -237,6 +237,7 @@ int PMIx_Init(pmix_proc_t *proc)
             (void)strncpy(proc->nspace, pmix_globals.myid.nspace, PMIX_MAX_NSLEN);
             proc->rank = pmix_globals.myid.rank;
         }
+        ++pmix_globals.init_cntr;
         return PMIX_SUCCESS;
     }