Fix typo in docker images

Change-Id: I1b432afe6725e0b6d99a448569db4c40837fad37
diff --git a/jenkins/client/job/docker.yml b/jenkins/client/job/docker.yml
index 220176c..f87dcf4 100644
--- a/jenkins/client/job/docker.yml
+++ b/jenkins/client/job/docker.yml
@@ -44,7 +44,7 @@
                 default: "tcpcloud/{{name}}"
               IMAGE_GIT_URL:
                 type: string
-                default: ${_param:jenkins_gerrit_url}/mk/docker-{{name}}"
+                default: "${_param:jenkins_gerrit_url}/mk/docker-{{name}}"
               IMAGE_BRANCH:
                 type: string
                 default: "{{branch}}"