ipvs: Allow heterogeneous pools now that we support them

Remove the temporary consistency check and add a case statement to only
allow ipip mixed dests.

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