New multi-scheduler code, uses SDB for locking
Addressing synfinatic comments
Added 'expiry' to lock, per sinfinatic's comment

I ended up keeping timestamp to represent the last time the lock was
changed, I think that's useful for the expected_values stuff in SDB's
writes.
New lock config settings
Locking code for the scheduler
Quiet down logging a bit, remove release method

This type of lock isn't meant to be released regularly, it's meant to
expire naturally when it's expire time runs out.
No longer need sub-class release method
Fix invalid super call
Remove release logic, mix up sleep times

Allows the backup host to take over more quickly in the case of a
failure.