MB-100 Start ns_ssl_proxy as permanent application.

So that if it terminates for some reason, entire VM is also
terminated.

Change-Id: Ie9c040f83c26e5d07eba53d56fe0fab6cb4892d4
Reviewed-on: http://review.couchbase.org/31752
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>