Repair rcenable(8) and rcdisable(8).

Repair rcenable(8) and rcdisable(8).

* rcenable(8) was not playing nicely with our three year old change to
  no longer depend on _enable being appended to rc variables for starting
  daemons etc. (i.e., foo_enable=yes and foo=yes both work).

* rcdisable(8) did not properly run rcstop(8) because that needs to be
  run when the variable is still set to 'yes' and not after it's been
  set to 'no'.

Noticed-by: phma on #dragonflybsd