Fix gerrit its-storyboard build

The build was failing because it was attempting to clone its-base
plugin with the same branch as the gerrit core.  This will typically
work for upstream builds but since we have a fork of gerrit core
(our own branch[1]) it doesn't work.  This change lets us configure
which branch to clone from, in this case just clone from the same
branch[2] as the plugin.

[1] http://git.openstack.org/cgit/openstack-infra/gerrit/log/?h=openstack/2.11.4
[2] https://gerrit.googlesource.com/plugins/its-base/+/stable-2.11

Change-Id: Ie20ef8f6e9f4500772bcc16f305c9c9e6466c44e

jenkins/jobs/gerrit-plugin-jobs.yaml

@@ -18,7 +18,7 @@
           git clone -b {gerrit-branch} {gerrit-project}
           PLUGIN_PARENT_PROJECT={plugin-parent-project}
           if [ -n "$PLUGIN_PARENT_PROJECT" ]; then
-            git clone -b {gerrit-branch} {plugin-parent-project} gerrit/plugins/{plugin-parent-name}
+            git clone -b {plugin-parent-branch} {plugin-parent-project} gerrit/plugins/{plugin-parent-name}
           fi
           git clone -b {plugin-branch} {plugin-project} gerrit/plugins/{plugin-name}
           cd gerrit/plugins/{plugin-name}

jenkins/jobs/projects.yaml

@@ -2014,6 +2014,7 @@
     gerrit-project: 'https://git.openstack.org/openstack-infra/gerrit'
     plugin-parent-name: ''
     plugin-parent-project: ''
+    plugin-parent-branch: ''
 
     jobs:
       - '{plugin-name}-gerrit-plugin-{plugin-branch}':
@@ -2037,9 +2038,10 @@
           gerrit-branch: 'openstack/2.11.4'
           plugin-name: 'its-storyboard'
           plugin-project: 'https://gerrit.googlesource.com/plugins/{plugin-name}'
+          plugin-branch: 'stable-2.11'
           plugin-parent-name: 'its-base'
           plugin-parent-project: 'https://gerrit.googlesource.com/plugins/{plugin-parent-name}'
-          plugin-branch: 'stable-2.11'
+          plugin-parent-branch: '{plugin-branch}'
 
 - project:
     name: gerrit-dash-creator