Add postgresql dev package as testonly neutron dep

The neutron functional job needs to build psycopg2 which has a
dependency on postgresql dev packages.

Change-Id: Ie5c8e2bd02e148d6638f4a4c1fbf6667c30313d5
diff --git a/files/rpms-suse/neutron b/files/rpms-suse/neutron
index 50ee145..66d6e4c 100644
--- a/files/rpms-suse/neutron
+++ b/files/rpms-suse/neutron
@@ -5,6 +5,7 @@
 iptables
 iputils
 mariadb # NOPRIME
+postgresql-devel        # testonly
 python-eventlet
 python-greenlet
 python-iso8601