Travis: Use Cassandra v3.11.4
Travis: Use Cassandra v3.11.4

Bug: T200803

milimetric/restbase,cscott/restbase,wikimedia/mediawiki-services-restbase,Pchelolo/restbase,wikimedia/restbase,cscott/restbase,wikimedia/restbase,milimetric/restbase,d00rman/restbase,d00rman/restbase,wikimedia/mediawiki-services-restbase,Pchelolo/restbase