files: Split ghost collecting routine

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
files: Support ghost devices

When we have opened and unlinked chr or blk device, we
shouls also take care of their rdev value. Thus -- new
field in image and some new steps on dump and restore.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
zdtm: Fix deleted_dev and add to the runlist

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
zdtm: Add more verbosity to deleted_dev failure

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>