ipvs: Pass destination address family to ip_vs_trash_get_dest

Part of a series of diffs to tease out destination family from virtual
family.  This diff just adds a parameter to ip_vs_trash_get and then uses
it for comparison rather than svc->af.

Signed-off-by: Alex Gartrell <agartrell@fb.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>