Added with_lock context manager for any lock
CassScalingGroup using kazoo lock

- setting kz_client to store after kazoo starts
- removed references to basiclock
- updated tests accordingly
with_lock tests added
Kazoo threads is configurable

Setting 100 threads in config.json since each lock operation requires a
thread access
Merge branch 'master' into kazoo_lock
fixed tests
tests updated for store.kz_client check
Merge pull request #467 from rackerlabs/kazoo_lock

Kazoo lock