The built lwtunnel_state struct has to be freed after comparison.

Fixes: 571e7226 ("ipv4: support for fib route lwtunnel encap attributes")
Signed-off-by: NJiri Benc <jbenc@redhat.com>
Acked-by: NRoopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>