MB-12358: disable ssl v3 for xdcr ssl proxy

Change-Id: I6d8ea4ccf47ce3c39aceff44682072e09561a50f
Reviewed-on: http://review.couchbase.org/42209
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>