define jenkins credentials for auth

to avoid issues with broken drivetrain from-the-box

prefix 'oss' defined to avoid naming-duplication with jenkins backend

Change-Id: I855dc71a45aa80d471d2f75435d68cd7370c8609
diff --git a/docker/swarm/stack/jenkins/master.yml b/docker/swarm/stack/jenkins/master.yml
index e974dee..96d4e10 100644
--- a/docker/swarm/stack/jenkins/master.yml
+++ b/docker/swarm/stack/jenkins/master.yml
@@ -6,6 +6,8 @@
     jenkins_master_extra_opts: ""
     jenkins_master_executors_num: 4
     jenkins_master_max_concurent_requests: 40
+    oss_jenkins_user: admin
+    oss_jenkins_password: password
   docker:
     client:
       stack: