datpath: Fix memory leak when a loop is detected.

datpath: Fix memory leak when a loop is detected.

If we detect a packet that is looping we kill the flow but then
don't do anything with the packet that caused the problem in the
first place, so this frees the packet.  This isn't a very serious
leak because we try to shut off the flow that lead to the loop
as early as possible.  Once this happens, packets will no longer
hit the loop detector and will be freed just as any other packet
that should be dropped.

It also fixes an issue where the offset to the stats counter is
uninitialized after a loop is detected.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>