MB-100: Remove EP_NO_PERSISTENCE env variable

We don't use this and have other ways of stopping persistence on
the server.

Change-Id: I303b713ddec24d6e2013b41f962b65da0aaf2949
Reviewed-on: http://review.couchbase.org/27154
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>