Merge remote-tracking branch 'ep-engine/watson' into kv_engine/watson_ep

Fixup commit to being ep-engine/watson and kv_engine/watson_ep into
alignment - they alreadyed contained the same code; however the last
couple of patch migrations from ep-engine/watson -> kv_engine were
incorrectly done as cherry-picks and hence the SHAs are not matching.

* ep-engine/watson:
  MB-25464: Do not exit cbstats if stats_perform fails
  MB-25238: Add logging to destruction of store
  [BP] MB-25337: Handle the vbucket state change gracefully during rollback

Change-Id: Iadeb180f1fa199ac1965047e25532612028e1b1c

Author: daverigby