Stop all neutron-ns-metadata-proxy with stop_neutron

Process name is actually python therefore neutron-ns-metadata-proxy
pattern didn't match wanted process.

Closes-bug: #1269982
Change-Id: Ib4439b0d32f103253b461841fa903c65763ff280
diff --git a/lib/neutron b/lib/neutron
index 960f11b..f9ee484 100644
--- a/lib/neutron
+++ b/lib/neutron
@@ -505,7 +505,7 @@
         [ ! -z "$pid" ] && sudo kill -9 $pid
     fi
     if is_service_enabled q-meta; then
-        sudo pkill -9 neutron-ns-metadata-proxy || :
+        sudo pkill -9 -f neutron-ns-metadata-proxy || :
     fi
 
     if is_service_enabled q-lbaas; then