Extract bonding options building into a separate function.

To make setupNetworks shorter, move the bonding options building code
into a separate function.

Signed-off-by: Mark Wu <wudxw@linux.vnet.ibm.com>
Change-Id: I77fefefcefa05f5bd0d7fa2755357d88b7aa615e
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/8885
Reviewed-by: Dan Kenigsberg <danken@redhat.com>