static-routes: Fixes bug12763

static-routes: Fixes bug12763

- This ensures that all ip route and ip rule commands are redirected to null if the output
   is not used to feed into a variable.
- This will prevent any error messages related to empty iproute tables being displayed
   during boot.
- Tested on my vm system and confirmed that the fix in ipsec-interfaces stops the "FIB
   table does not exist" and "RTNETLINK answers: no such file or directory" messages during
   boot.

Fixes: Bug#12763
Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>