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: I7b91b4e67594ce62772e3e450a1236095d4ef1c9

hiera/group/zuul-executor.yaml

@@ -11,5 +11,9 @@ zuul_connections:
     driver: 'github'
 
   - name: 'googlesource'
-    driver: 'git'
+    driver: 'gerrit'
-    baseurl: https://gerrit.googlesource.com
+    server: 'gerrit-review.googlesource.com'
+    canonical_hostname: 'gerrit.googlesource.com'
+    user: 'git-infra-root.openstack.org'
+    stream_events: 'false'
+    auth_type: 'basic'

hiera/group/zuul-merger.yaml

@@ -41,5 +41,9 @@ zuul_connections:
     driver: 'github'
 
   - name: 'googlesource'
-    driver: 'git'
+    driver: 'gerrit'
-    baseurl: https://gerrit.googlesource.com
+    server: 'gerrit-review.googlesource.com'
+    canonical_hostname: 'gerrit.googlesource.com'
+    user: 'git-infra-root.openstack.org'
+    stream_events: 'false'
+    auth_type: 'basic'

hiera/group/zuul-scheduler.yaml

@@ -31,8 +31,12 @@ zuul_connections:
     rate_limit_logging: 'false'
 
   - name: 'googlesource'
-    driver: 'git'
+    driver: 'gerrit'
-    baseurl: https://gerrit.googlesource.com
+    server: 'gerrit-review.googlesource.com'
+    canonical_hostname: 'gerrit.googlesource.com'
+    user: 'git-infra-root.openstack.org'
+    stream_events: 'false'
+    auth_type: 'basic'
 
 gearman_server_ssl_cert: |
   -----BEGIN CERTIFICATE-----