MB-9839 Pass ns_ssl_proxy environment via OS environment variable.

Because on windows erlang fails to escape arguments for child process
correctly.

Change-Id: I19fa03b760f300dbf26d42204f097e061a972eb6
Reviewed-on: http://review.couchbase.org/31753
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>