Prevent open FIFO prom leaking to subprocess
Prevent open FIFO prom leaking to subprocess

This fix previews window staying open after nnn exits, because they
inherited open FIFO (in write mode) from parent nnn process, and never
close it.

jarun/noice,jarun/nnn,jarun/nnn,jarun/nnn,jarun/nnn,jarun/noice