Add option to edit ceilometer notification topics

To enable OSprofiler we should be able to add "profiler" notification
topic to ceilometer notification topics.

It won't add any overhead to Ceilometer until we start
using OSprofiler.

To use OSprofiler we have to add special trace information in
request headers that will produce actually trigger profiler,
that will send bunch of notifications.

This mostly will be used by Rally, and probably one of
Tempest job, after we integrate osprofiler to tempest.

More about osprofiler:
https://github.com/stackforge/osprofiler

Change-Id: I78bb3f8cbe211b5233ab9645718099d521f9b10b

devstack-vm-gate.sh

@@ -227,6 +227,13 @@ EOF
         # that run under HTTPD (mod_wsgi) by default.
         echo "ENABLE_HTTPD_MOD_WSGI_SERVICES=False" >> localrc
     fi
+
+    if [[ "$CEILOMETER_NOTIFICATION_TOPICS" ]]; then
+        # Add specified ceilometer notification topics to localrc
+        # Set to notifications,profiler to enable profiling
+        echo "CEILOMETER_NOTIFICATION_TOPICS=$CEILOMETER_NOTIFICATION_TOPICS" >>localrc
+    fi
+
     if [[ "$DEVSTACK_GATE_TEMPEST_NOVA_V3_API" -eq "1" ]]; then
         echo "TEMPEST_NOVA_API_V3=True" >> localrc
     fi