Use app instances if label is unavailable in ZDD. (#396)
Use app instances if label is unavailable in ZDD. (#396)

This fixes #393.
mesosphere/marathon-lb,vixns/marathon-lb,vixns/marathon-lb,mesosphere/marathon-lb,matt-deboer/marathon-lb,vixns/marathon-lb,mesosphere/marathon-lb,matt-deboer/marathon-lb,matt-deboer/marathon-lb