network: support multiple bonding interfaces

network: support multiple bonding interfaces

Currently dracut only support 1 bond, namyly bond0 by default. However multiple
bonds configuration may be needed. For example in kdump, in 1st kernel, more
than one bonds may be configured, and bondX other than bond0 is used as output
interface to remote host which will store dump core. This patch can solve this
problem, to write real bond information to initramfs, 2nd kdump kernel will
use it to create the relevant bondX interface.

Tested-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Baoquan He <bhe@redhat.com>