service: Fix retriggering of init.d-scripts.

service: Fix retriggering of init.d-scripts.

Fix retriggering of init.d-scripts which calls
commands dependent on functional STDIN/STDOUT/STDERR.

If we just close these file descriptors those commands
will not work as expected leading to unwanted
consequences. If we instead redirect the file descriptors
to /dev/null, we will end up the same end-result and these
commands will work as expected.

Signed-off-by: Markus Gothe <markus.gothe@genexis.eu>
Signed-off-by: Felix Fietkau <nbd@nbd.name> [refactor]