dracut: add team device support

dracut: add team device support

V2: merge patch 2/2
    fix active-backup mode by adding slaves one by one
    sync with the latest teamd
    improve the comments
    wait for team ports to come up
    install /etc/libnl/classid too

This patch adds the initial support for team device [1].
A new cmdline team= is introduced for it.

Note, currently we don't support stacked devices
on/under team, it is tricky and can be added on request.

1. http://www.libteam.org/

Cc: Harald Hoyer <harald@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <amwang@redhat.com>