Revert "Move ns_server and ep-engine to their respective 3.0.1 cherry-pick branches"

This reverts commit b2c8c660c5fdabc775923561899c97825681dc28.

Change-Id: I1191a54bf1f807d42d592752ca63968b079abdb7
Reviewed-on: http://review.couchbase.org/42721
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>