Merge branch 'jej/run-mysql-tests-on-stable-preparation-branches' into 'master'

Run mysql tests on stable preperation branches like 9-3-stable-patch-2

See merge request !12552

.gitlab-ci.yml

@@ -63,7 +63,7 @@ stages:
 .only-master-and-ee-or-mysql: &only-master-and-ee-or-mysql
   only:
     - /mysql/
-    - /-stable$/
+    - /-stable/
     - master@gitlab-org/gitlab-ce
     - master@gitlab/gitlabhq
     - tags@gitlab-org/gitlab-ce