STASHDEV-7996: Drain local member

STASHDEV-7996: Added drain method to PartitionService interface. In the client this simply returns. In the cluster member it removes the PARTITION_HOST Capability from the local member and awaits for all partitions owned by the local member to migrate. If the local node is the only member returned by getPartitionHosts then we assume the data cannot be drained.
I think its worth adding a comment about why you are bailing early here.