netfilter: flowtable: fixup UDP timeout depending on ct state

Currently flow_offload_fixup_ct() function assumes that only replied UDP
connections can be offloaded and hardcodes UDP_CT_REPLIED timeout value. To
enable UDP NEW connection offload in following patches extract the actual
connections state from ct->status and set the timeout according to it.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>