Use the gerrit driver for the googlesource connection

This is the connection for Gerrit's Gerrit.  We can connect to it
directly with the Gerrit driver now that we support entirely
HTTP-based Gerrits and we have an account.  Use that so we can
set up some third-party CI testing.

Change-Id: I10e279218de985a0c17ea6b5bc46f3eebefcfb39

hiera/group/zuul-executor.yaml

@@ -11,5 +11,8 @@ zuul_connections:
     driver: 'github'
 
   - name: 'googlesource'
-    driver: 'git'
-    baseurl: https://gerrit.googlesource.com
+    driver: 'gerrit'
+    server: 'gerrit-review.googlesource.com'
+    canonical_hostname: 'gerrit.googlesource.com'
+    user: 'git-infra-root.openstack.org'
+    stream_events: 'false'

hiera/group/zuul-merger.yaml

@@ -41,5 +41,8 @@ zuul_connections:
     driver: 'github'
 
   - name: 'googlesource'
-    driver: 'git'
-    baseurl: https://gerrit.googlesource.com
+    driver: 'gerrit'
+    server: 'gerrit-review.googlesource.com'
+    canonical_hostname: 'gerrit.googlesource.com'
+    user: 'git-infra-root.openstack.org'
+    stream_events: 'false'

hiera/group/zuul-scheduler.yaml

@@ -31,8 +31,11 @@ zuul_connections:
     rate_limit_logging: 'false'
 
   - name: 'googlesource'
-    driver: 'git'
-    baseurl: https://gerrit.googlesource.com
+    driver: 'gerrit'
+    server: 'gerrit-review.googlesource.com'
+    canonical_hostname: 'gerrit.googlesource.com'
+    user: 'git-infra-root.openstack.org'
+    stream_events: 'false'
 
 gearman_server_ssl_cert: |
   -----BEGIN CERTIFICATE-----