orte/util/nidmap.c: fix uninitialized variable

Squash compiler warning.

Signed-off-by: William Bailey <wbailey2@nd.edu>

orte/util/nidmap.c

@@ -1123,7 +1123,7 @@ int orte_util_decode_ppn(orte_job_t *jdata,
 {
     orte_std_cntr_t index;
     orte_app_idx_t n;
-    int cnt, rc, m;
+    int cnt, rc=0, m;
     opal_byte_object_t *boptr;
     bool compressed;
     uint8_t *bytes;