NAT: Fixed issues with dropping reverse packets with output-feature.

Fixed NAT issues with dropping reverse packets in case NAT worked
in 'endpoint-dependent' mode and outside interface has FIB different
from 0 when the output-feature is set.

In this case, the out2in_ed dynamic hash key was not being created
correctly.

Change-Id: I6362967f4b09a375a4606eedaa8e264795b25453
Signed-off-by: Dmitry Vakhrushev <dmitry@netgate.com>