Fix shell for keystone user for rsync to work

Fix shell for keystone user to /bin/bash for rsync to work
between control nodes for fernet and credential keys sync.
Generally keystone should be created by linux formula since user
definition is present in reclass

Change-Id: I6ed8e28849ef00804fae9af3b77a83778dcf1972
Related-PROD: PROD-22887
diff --git a/keystone/server.sls b/keystone/server.sls
index 96adc87..1d691e3 100644
--- a/keystone/server.sls
+++ b/keystone/server.sls
@@ -80,7 +80,7 @@
     - home: /var/lib/keystone
     - uid: 301
     - gid: 301
-    - shell: /bin/false
+    - shell: /bin/bash
     - system: True
     - require_in:
       - pkg: keystone_packages