ofproto-dpif-xlate: Fix memory leak in execute_controller_action.

ofproto-dpif-xlate: Fix memory leak in execute_controller_action.

commit df70a7731 ("ofproto-dpif-xlate: Allow translating
without side-effects.") created a memory leak by removing the
dp_packet_delete statement in execute_controller_action that
freed the earlier cloned packet.  This commit restores this
statement to the end of the method.

Fixes: df70a7731 ("ofproto-dpif-xlate: Allow translating without side-effects.")
Signed-off-by: Ryan Moats <rmoats@us.ibm.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>