Only start zeromq-receiver when we're using zeromq.

Change-Id: Ibd3e6a74f1098e330be0fcbbb83b9188e51202ad
diff --git a/stack.sh b/stack.sh
index cfce6be..0407c30 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1017,7 +1017,10 @@
     iniset $NOVA_CONF DEFAULT s3_affix_tenant "True"
 fi
 
-screen_it zeromq "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-rpc-zmq-receiver"
+if is_service_enabled zeromq; then
+    echo_summary "Starting zermomq receiver"
+    screen_it zeromq "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-rpc-zmq-receiver"
+fi
 
 # Launch the nova-api and wait for it to answer before continuing
 if is_service_enabled n-api; then