Set gerrit digest auth in zuul config

Zuul is updating the default auth type for gerrit connections to better
reflect current Gerrit's expectations. We need to force digest instead
of basic auth in order to accomodate our older gerrit install.

Change-Id: I6ec64f0625abe0c9e3871a5d1942a35e1a58177c

hiera/group/zuul-executor.yaml

@@ -6,6 +6,7 @@ zuul_connections:
     canonical_hostname: 'opendev.org'
     user: 'zuul'
     sshkey: '/var/lib/zuul/ssh/id_rsa'
+    auth_type: 'digest'
 
   - name: 'github'
     driver: 'github'

hiera/group/zuul-merger.yaml

@@ -36,6 +36,7 @@ zuul_connections:
     canonical_hostname: 'opendev.org'
     user: 'zuul'
     sshkey: '/var/lib/zuul/ssh/id_rsa'
+    auth_type: 'digest'
 
   - name: 'github'
     driver: 'github'

hiera/group/zuul-scheduler.yaml

@@ -14,6 +14,7 @@ zuul_connections:
     user: 'zuul'
     sshkey: '/var/lib/zuul/ssh/id_rsa'
     gitweb_url_template: 'https://opendev.org/{project.name}/commit/{sha}'
+    auth_type: 'digest'
 
   - name: 'opendaylight'
     driver: 'gerrit'