Add sanity check framework to verify neutron server/backend integration

Some Neutron plugins require controllers and multiple backend services
to operate correctly. This patch adds the framework for third party
plugins to run sanity checks after Neutron Server has started.

This simple addition may reveal potential configuration pitfalls
much earlier in the dev/test cycle, thus speeding up the build
churn process.

The first plugin that uses this framework is the VMware NSX one.

Closes-bug: #1265671

Change-Id: I17f9c5c8e828316ff03f0eff42ae4ae6c6c58733
diff --git a/stack.sh b/stack.sh
index 7da41a9..621a058 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1116,6 +1116,7 @@
 if is_service_enabled q-svc; then
     echo_summary "Starting Neutron"
     start_neutron_service_and_check
+    check_neutron_third_party_integration
 elif is_service_enabled $DATABASE_BACKENDS && is_service_enabled n-net; then
     NM_CONF=${NOVA_CONF}
     if is_service_enabled n-cell; then