Merge commit 'd3d4f2032a66a9fe91ba5b4ceca114b4690330f5'
Merge branch 'resharding'
Improved transaction error handling.
Merge branch 'master' of github.com:youtube/vitess
Improved transaction error handling.
Merge branch 'barnacle'
Make vttablet connection a plugin.
Simplified query service state machine.

Got rid of CLOSED state, renamed OPEN to SERVING to mirror the
NOT_SERVING state. Also, DisallowQueries does not take a forRestart
flag any more. Query service always returns RETRY during (and after)
shutdown.
Merge branch 'master' into barnacle
Improved shard_conn retries.
Drop connect from shard_conn.
Sandbox strawman for barnacle testing.
Tests for shard_conn using sandbox.
Add time check for tx_pool_full test.
Fixing topology tee.

We had missed:
- the tablet updates need to keep a version map
- need to protect member variables with mutex
- implementing the tablet action parts.
Merge branch 'master' into resharding