Refactor MutationLogCompactor task

Change-Id: I21de542882121e43dc8764e139c089c7c51c7d1b
Remove concurrency related parameters from couchstore

Thes parameters will be decided at a higher level in the future
so it doesn't make sense to have them anymore. I am also not
aware of anyone who would want to use them or does currently
use them.

Change-Id: I117fe499dac868352084854ae1cdad992971be76
Add the iomanager

Change-Id: I0766f6f9ad597c35f85f9af69494873b329ac193
Moved the VBucketDelete Task

Change-Id: I96041520870eef0dbd4c7714c9a3eaac7e658f08
Fix all of the bugs related to previous work

Change-Id: Ib8ade98fec1fc768df48f25a0d5d83a44b69ca4e
Move the StatsSnap task into the new dispatcher model

Change-Id: Ie4bba2dedbb99ba4f8d3f61ebf7b88618b880805
Move the MutationLogCompactor task into the new Dispatcher

Change-Id: Ieb6199d2edb7c9578a0e9b574772c6974a79593f
Cleanup of new iomanager

Change-Id: Iccaa2c027cdb9abdd6c580973f94ee6d254ef035