Add stable-2.15 to lfs plugin

Change-Id: Icfddea10259638823e2a4fe30dc6e7c5f748d68b
diff --git a/jenkins/gerrit-buck-bazel-plugin-lfs.yaml b/jenkins/gerrit-buck-bazel-plugin-lfs.yaml
index e1075e6..27de9f2 100644
--- a/jenkins/gerrit-buck-bazel-plugin-lfs.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-lfs.yaml
@@ -7,4 +7,5 @@
       - 'plugin-{name}-bazel-{branch}':
           branch:
             - master
+            - stable-2.15
             - stable-2.14