Revert "MB-9480: Revert "MB-9457: pass swt low to child erlang""

This reverts commit 811b6f15011301018a6ba25e74c18ec36dad97c3.

And returns +swt low back by default.

Change-Id: Ief0d93b95f07d619ef3ebf34bdc5d119f20e0130
Reviewed-on: http://review.couchbase.org/33516
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>