Update bbsim-tests validBranches for 2.15 release

Signed-off-by: Eric Ball <eball@linuxfoundation.org>
Change-Id: Id2f7617af4e9ae083382a01d9639265067d0a349
diff --git a/jjb/pipeline/voltha/bbsim-tests.groovy b/jjb/pipeline/voltha/bbsim-tests.groovy
index d8b50b9..2ccc319 100644
--- a/jjb/pipeline/voltha/bbsim-tests.groovy
+++ b/jjb/pipeline/voltha/bbsim-tests.groovy
@@ -37,7 +37,7 @@
 //   as a guarantee release jobs are running in an expected sandbox.
 // -----------------------------------------------------------------------
 String branchName() {
-    def validBranches = ["master", "voltha-2.14"]
+    def validBranches = ["master", "voltha-2.15"]
 
     // "${branch}" is assigned by jenkins
     if (!validBranches.contains(branch)) {