Fixed branch-regexp for voltha-2.8 patchset verification jobs

Change-Id: I28d80a025513df39e8dc2debd616248b8cba8465
diff --git a/jjb/verify/bbsim-sadis-server.yaml b/jjb/verify/bbsim-sadis-server.yaml
index a5c90cf..fea3a4b 100644
--- a/jjb/verify/bbsim-sadis-server.yaml
+++ b/jjb/verify/bbsim-sadis-server.yaml
@@ -10,7 +10,7 @@
           branch-regexp: '{all-branches-regexp}'
       - 'verify-bbsim-sadis-server-jobs-voltha-2.8':
           name-extension: '-voltha-2.8'
-          branch-regexp: '{kind-voltha-regexp}'
+          branch-regexp: '^voltha-2.8$'
       - 'verify-bbsim-sadis-server-jobs-master':
           branch-regexp: '^master$'
       - 'publish-bbsim-sadis-server-jobs':