dhclient-script: fix bound

dhclient-script: fix bound

When we get a BOUND we should have only new_* variables set.
So it is stated in the manpage.
Apparently, also old_* variables are set so we never got into the block where the IP address was set.
We now always set a new IP Address when we get a BOUND.

Fixes: #11363
Signed-off-by: Jonatan Schlag <jonatan.schlag@ipfire.org>
Signed-off-by: Jonatan Schlag &lt;<a href="mailto:jonatan.schlag@ipfire.org">jonatan.schlag@ipfire.org</a>&gt;
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>