networking: Allow changing DHCP Option Rapid Commit

networking: Allow changing DHCP Option Rapid Commit

This option needs to be configurable since some (braindead) ISPs have
started running broken DHCP servers to be bug-compatible with cheap
broken plastic routers.

By default we keep this option enabled, but it can now be turned off
whenever needed.

Suggested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>