Be more flexible with addresses in ZkOccConnection.

Allow the set of zkocc hosts to be updated. Also, limit the number of
dial attempts for any given operation - this is useful when the set of
zkocc hosts gets large.
Add -follow flag for zkctl and mysqlctl.
Running zkctl in Docker.
Rename to 'refresh' since 'update' is a semantically loaded term in Python.
Refactoring MigrateServedFrom to split master and regular cases.
New simpler faster logic for masterMigrateServedFrom.

We dont' set the source master read-only any more, just use
blacklisted tables to achieve the same result.
Merge pull request #85 from plobsing/zkocc-conn-addrs

Zkocc conn addrs
Fail fast and report errors when parsing zk config files.
Fixing a couple comments from the review.
Merge branch 'master' of github.com:youtube/vitess
Running action callbacks synchronously now.

Since everything is RPCs, it's better that way really.
Adding error returns to a few methods.
Better comments.
Merge branch 'master' into replication
Allowing ShardReplicationFix to remove a misplaced tablet.

Also more logging in wrangler.
Better HTML so it displays right.
Logging an action to the right place.
Adding SplitShardCount to Keyspace and SrvKeyspace.

Not used by any client yet. Can be changed with SetShardingInfo.
Changing served-from to served_from, new standard.