Build serviceuser plugin stable-3.{4,5,6} branches

Change-Id: I18a65c363b7e46bc6ad2a7dc7ed297347a010c5a
diff --git a/jenkins/gerrit-bazel-plugin-serviceuser.yaml b/jenkins/gerrit-bazel-plugin-serviceuser.yaml
index 7fd1c78..0fc18ea 100644
--- a/jenkins/gerrit-bazel-plugin-serviceuser.yaml
+++ b/jenkins/gerrit-bazel-plugin-serviceuser.yaml
@@ -5,8 +5,10 @@
           branch:
             - master
           gerrit-branch:
-            - master
             - stable-3.7
+      - 'plugin-{name}-bazel-{branch}':
+          branch:
+            - master
             - stable-3.6
             - stable-3.5
             - stable-3.4