Fixed regular expression for gerrit tests triggering

Change-Id: I312eb6c6e05085d65445885d1b488f66cb78cfe1
diff --git a/jenkins/client/job/opencontrail/build/test.yml b/jenkins/client/job/opencontrail/build/test.yml
index 0d1f7bf..efb09f9 100644
--- a/jenkins/client/job/opencontrail/build/test.yml
+++ b/jenkins/client/job/opencontrail/build/test.yml
@@ -64,7 +64,7 @@
                 event:
                  comment:
                     - addedContains:
-                        commentAddedCommentContains: "^(test|recheck|reverify)$"
+                        commentAddedCommentContains: '^(?s:Patch Set \d+:\s*(test|recheck|reverify)\s*)$'
             param:
               TEST_MODELS:
                 type: string