Bump src/dea_next

Bump cloudfoundry/dea_ng:
  Aram Price:
     Remove unnecessary class hierarchy ( Travis Success: https://travis-ci.org/cloudfoundry/dea_ng/builds/16622471 )
     Stop using custom logger ( Travis Unknown )
     Fix quotes ( Travis Unknown )
     Log when staging fails ( Travis Unknown )
     Ensure that WardenError#inspect does not leak info ( Travis Unknown )