Build websession-broker plugin on stable-3.4 branch

Change-Id: I2af80d0fb68fece37444d2252e69a5c4389050f0
diff --git a/jenkins/gerrit-bazel-plugin-websession-broker.yaml b/jenkins/gerrit-bazel-plugin-websession-broker.yaml
index 9a08008..9a2dbb1 100644
--- a/jenkins/gerrit-bazel-plugin-websession-broker.yaml
+++ b/jenkins/gerrit-bazel-plugin-websession-broker.yaml
@@ -1,9 +1,14 @@
 - project:
     name: websession-broker
     jobs:
-      - 'plugin-{name}-bazel-{branch}':
+      - 'plugin-{name}-bazel-{branch}-{gerrit-branch}':
           branch:
             - master
+          gerrit-branch:
+            - master
+            - stable-3.4
+      - 'plugin-{name}-bazel-{branch}':
+          branch:
             - stable-3.3
             - stable-3.2
             - stable-3.1