MB-6595 Install mlockall stub correctly.

On platforms where the actual NIF is not built.

Change-Id: Iec69c19fefc016d451013a6fb649146b7fdcc7ae
Reviewed-on: http://review.couchbase.org/23993
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Revert "MB-7478: Identify few more trouble cases"

This reverts commit 461389779628088823e9ebe389004ed10161bd07.
Merge branch '2.0.1' of git://github.com/couchbase/ns_server into 2.0.1
MB-7478: Make few more tests pass