Change metal3 jobs trigger phrase pattern

Change-Id: If433df048028e4bb34c560ff029290305dff2d82
diff --git a/jjb/metal3/job_fullstack_building_test.yml b/jjb/metal3/job_fullstack_building_test.yml
index 5956785..918ce98 100644
--- a/jjb/metal3/job_fullstack_building_test.yml
+++ b/jjb/metal3/job_fullstack_building_test.yml
@@ -190,7 +190,7 @@
         org-list: "{ci_github_whitelist_org}"
         cron: 'H/5 * * * *'
         auth-id: "{ci_ghprb_auth_id}"
-        trigger-phrase: '((.|\n)*\s)?/test-metal3-fullstack(\s(.|\n)*)?'
+        trigger-phrase: '.*?/test-metal3-fullstack.*?'
         skip-build-phrase: '/skip-test'
         only-trigger-phrase: True
         github-hooks: True