CBD-485: Remove couch-kvstore TMPFAIL & retry logic

with compaction moved to ep-engine completely, we no longer
need this logic.

replaced it with asserts instead.

Change-Id: I23d98baaebd52728a77730942bb4cfb5551c834b
Reviewed-on: http://review.couchbase.org/36716
Reviewed-by: abhinav dangeti <abhinav@couchbase.com>
Tested-by: Sundararaman Sridharan <sundar@couchbase.com>