Connect jenkins slave via docker network on swarm

Update jenkins location url for that case only

Change-Id: Icc74e24a4a4343ba32ca3bd7e2c15e9ea0e5ca6c
Related-bug: PROD-26834
             PROD-30275
(cherry picked from commit 883d27ba078a56333bffa80b5f903a8596546c8a)
diff --git a/docker/swarm/stack/jenkins/master.yml b/docker/swarm/stack/jenkins/master.yml
index 4647521..ea4dfe5 100644
--- a/docker/swarm/stack/jenkins/master.yml
+++ b/docker/swarm/stack/jenkins/master.yml
@@ -31,3 +31,8 @@
               volumes:
                 - /srv/volumes/jenkins:/var/jenkins_home
                 - /etc/ssl/certs/java/cacerts:/etc/ssl/certs/java/cacerts:ro
+  # This is required only for deployments in swarm
+  jenkins:
+    client:
+      location:
+        url: http://jenkins_master:8080