NPF: fix the reference counting and share the active NAT portmap correctly
when performing the reload.  Should fixes PR/49412, reported by kardel@.
Appease gcc 4.8 - from Greg Willatt in private email.
Changes done in rsh.c rev. 1.35 was incomplete.  As chuq pointed
in private mail, it broke rcp(1).

To achieve the documented behavior and to fix long standing incorrect
rsh(1) behavior which I've tried to fix in rev. 1.35, rcmd(1) should have
two operation mode; whether it should relay signal information on
auxiliary channel or not, depending on the argument `fd2p' passed to rcmd(3).
So, make rcmd(1) behave differntly depending on the environment variable and
set it when necessary in rcmd(3) according to how auxiliary channel
is set up by rcmd(3).