Fix broken python client sharded.py
Merge branch 'master' into liguo

Conflicts:
	py/vtdb/sharded.py
Merge branch 'master' into liguo
Merge branch 'master' into liguo
Refactor vtdb client with connection lookup table
Fix integration tests
Merge branch 'master' of github.com:youtube/vitess
Merge commit 'c64eba62215f77e5af8f644dc8700a0f0c6a4a06'
Merge branch 'master' into replication