qemu.tests : Add new test boot_order_check

add new case boot_order_check

changes from v1:
1) update time.sleep to wait_for()
2) add some comments
3) modify replace ascii char(backspace)

changes from v2:
1) fix check whether guest is booted

changes from v3:
1) move boot_fail_infos to the cfg files
2) update the check branch

changes from v4:
1) update the TestFail info

changes from v5:
1) check the boot order by boot_fail_infos

changes from v6:
1) get the nic_addr from 'info pci'

chages from v7:
1) add func to get nic_addr from nic_device_id

Signed-off-by: Shuping Cui <scui@redhat.com>
Acked-by: Feng Yang <fyang@redhat.com>