network: Fix bonding opts

Previously the bonding opts were also written to the BOOTIF device even
if it wasn't a bond. This is now fixed and the bonding options are only
written ito the bonding configuration file.

Change-Id: I5b8a36c53dcd4f96ad83392c6e0be2ff8de660b9
Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>