defaults: Add default bond option

Add default bond option to avoid some issue when
auto install with "bond=bond0:eth1".

Change-Id: Idacb6dc570f6ecb3dff45c4d7349431973f549a2
Bug-Url:https://bugzilla.redhat.com/show_bug.cgi?id=1005741
Signed-off-by: hadong <hadong0720@gmail.com>