Build its-rtc for Gerrit 2.1{3,4,5}

Change-Id: Ic341ffc4c6f3050ca5790af8af09b2deb57d2f46
diff --git a/jenkins/gerrit-buck-bazel-plugin-its-rtc.yaml b/jenkins/gerrit-buck-bazel-plugin-its-rtc.yaml
index 7084313..1b02e6c 100644
--- a/jenkins/gerrit-buck-bazel-plugin-its-rtc.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-its-rtc.yaml
@@ -5,6 +5,11 @@
           branch:
             - stable-2.11
             - stable-2.10
-      - 'plugin-its-{name}-bazel-{branch}':
+      - 'plugin-its-{name}-bazel-{branch}-{gerrit-branch}':
           branch:
             - master
+          gerrit-branch:
+            - master
+            - stable-2.15
+            - stable-2.14
+            - stable-2.13