CBQE-1198: cleanup cache miss queues between runs

Change-Id: I2df1f6b0e799e1442923024496f6eb2b60e03688
Reviewed-on: http://review.couchbase.org/25522
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>