Cleanup MemcLockManager and move it to /libs

Cleanup MemcLockManager and move it to /libs

* Remove wf* function and ObjectCache dependencies.
* Use the base class session field.
* Lower physical lock structure TTL and move it to the base
  class as a constant.
* Resolve TODO about acquiring mixed lock types in one pass.
* Only mark servers down for 30 seconds in case of long-running
  scripts.

Change-Id: Icd4be407e599524cc620975d27e85666d2532b95