MB-10309 Disable mlockall in cluster_run.

I discovered that memory consumption problems that we saw on R16* go
away if I disable mlockall. I suspect that it has something to do with
mseg allocator overhaul that was part of R16 release. Since currently
we support R16 only for development, we can just disable mlockall in
cluster_run to mitigate the issue. Making us ready for production on
R16 would require more effort though.

Change-Id: Id2b9171add9601dcd6145687ddc9b0104bc4d14e
Reviewed-on: http://review.couchbase.org/34968
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>