Add a note about discovery service.
Add a note about discovery service.

apache/karaf-cellar,FlavioF/karaf-cellar,apache/karaf-cellar,albertocsm/karaf-cellar,mcculls/karaf-cellar,albertocsm/karaf-cellar,3cky/karaf-cellar,albertocsm/karaf-cellar,3cky/karaf-cellar,FlavioF/karaf-cellar,mcculls/karaf-cellar,FlavioF/karaf-cellar,3cky/karaf-cellar