config-check: fix invalid zuul.conf for gerrit_connections

The zuul.conf test configuration is missing the gerrit driver when
gerrit_connections are used

Change-Id: I482501c4d240950e5d30aa0b3cd8899daffd1064

config/ansible/roles/sf-jenkins/templates/zuul.conf.j2

@@ -7,6 +7,7 @@ user=jenkins
 
 {% for conn in gerrit_connections %}{% if not conn.disabled|default(False) %}
 [connection {{ conn.name }}]
+driver=gerrit
 server=localhost
 user=jenkins