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/lib/neutron b/lib/neutron
index 43f43f9..81faa10 100644
--- a/lib/neutron
+++ b/lib/neutron
@@ -958,6 +958,11 @@
     _neutron_third_party_do stop
 }
 
+# check_neutron_third_party_integration() - Check that third party integration is sane
+function check_neutron_third_party_integration() {
+    _neutron_third_party_do check
+}
+
 
 # Restore xtrace
 $XTRACE