guestfish_block_dev: Add 3 scrub related cases

1.scrub-device
2.scrub-device
3.scrub-freespace
guestfish_block_dev: Add md device related case

1. md-create
2. md-detail
3. md-stop
4. md-stat
5. list-md-devices
guestfish_block_dev: Add part_add, part_del, part_init cases
Add test cases for:
    1. Attach disk of special disk name
    2. Audit log check after detach
    3. Disk type check after attach
Improve disk hotplug/hotunplug audit test.
Improve audit check function.
guestfish_block_dev: Add cases to test API

part-set-bootable
part-get-bootable
part-set-mbr-id
part-get-mbr-id
Merge pull request #126 from vanbogithub/bfan-dev

Add some scrub and md device related cases
Merge pull request #130 from rbian/master

Add test cases for virsh at/dttach-disk:
vol_create: Update specific error msg for skip cases

As test on rhel7 with rhev qemu, the error msg is different from
upstream qemu, so update the error msg which from qemu-img to
skip unsupported img type cases.

Signed-off-by: Wayne Sun <gsun@redhat.com>