Implemented re-resolve on error for topology and added tests.
removed superfluous line from test.
Cleanup for readability and corresponding changes to tests.
Minor cleanup for readability.
First pass at vttablet health check.

Moving a lot of stuff around too.
Implementing rebuild for tablet health.
Merge branch 'vtocc'
Adding test for health check.

And fixing associated bugs.
Comment fix.
Health modules: initial version of the framework.
Health checks for MySQL.
Only accepting spare to target state changes.
Merge branch 'master' into replication
Integrating with Ric's change.
Finishing integration.
Backported the fix I had made in third_party.
Merge branch 'master' into vtocc
Merge branch 'master' into vtocc