Changes to rs-mysql

- Skip verifying slave if the timeout is set to a negative number.
  This helps in running tests using test-kitchen.
- Upgrade test-kitchen.
- README.md fixes.
- Rename rs-mysql::server to rs-mysql::default.
- Separate collectd monitoring specific stuff to rs-mysql::collectd.
- Remove unused `close` method from spec helpers.
Use the concurrency flag for kitchen.