Cluster: I/O errors are now logged at DEBUG level.
redis-trib: set the migrating slot in the correct way when resharding.
Cluster: ASKING command fixed, state was not retained.
Cluster: new command flag forcing implicit ASKING.

Also using this new flag the RESTORE-ASKING command was implemented that
will be used by MIGRATE.
Use RESTORE-ASKING for MIGRATE when in cluster mode.
Cluster: always use cluster(Add|Del)Slot to modify the cluster slots table.
Cluster: clusterAddSlot() was not doing what stated in the comment.
redis-trib: some refactoring and skeleton of the "fix" command.
redis-trib: move instance vars in the right class.
Aesthetic change to make a line more 80-cols friendly.
Call clusterUpdateState() after CLUSTER SETSLOT too.
Cluster: more correct update of slots state when PONG is received.
redis-trib: fixed typo in method name.
redis-trib: ability to fix uncovered slots for the trivial case.
redis-trib: specify single node address when fixing coverage.
Cluster: empty the internal sorted set mapping keys to slots on FLUSHDB/ALL.
Cluster: fix case of slotToKey...() functions.
redis-trib: handle slot coverage fix in the "no nodes with keys" case.
redis-trib: skeleton of coverage fix for "keys in multiple nodes" case.
redis-trib: check that all the nodes agree about the slots configuration.