MB-20697: ep_testsuite: restore deleted DB dir before cleanup
MB-20697: ep_testsuite: restore deleted DB dir before cleanup

In some environments (seen on Windows VM), the regression test for
MB-20697 can hang forever during cleanup due to the writer thread being
stuck in an infinite loop trying to flush to disk.

To address this, re-create the database directory before shutting down
EPStore (after the test is complete).

Change-Id: I474e77bafbe5b30858d9a306669c52713890f846
Reviewed-on: http://review.couchbase.org/67681
Reviewed-by: Daniel Owen <b3fc0e1a51f252986e60be7da121b74d3ac6845f@couchbase.com>
Reviewed-by: Manu Dhundi <158873d90a7ef40f3637a222b7329c09d0222554@couchbase.com>
Well-Formed: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

membase/ep-engine,membase/ep-engine,couchbase/ep-engine,daverigby/ep-engine,daverigby/kv_engine,couchbase/ep-engine,daverigby/ep-engine,daverigby/ep-engine,daverigby/kv_engine,membase/ep-engine,membase/ep-engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/ep-engine,couchbase/ep-engine,couchbase/ep-engine