MB-6368: Remove multiple variable tracking warmup status

Change-Id: I3aefc055d15c396c84fd7997f46cdf8b7c5c51b3
Reviewed-on: http://review.couchbase.org/24799
Tested-by: Michael Wiederhold <mike@couchbase.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>