qemu: Add new test check block size

Check physical block size and logical block size for virtio block device:
1) Install guest with a new image.
2) Verify whether physical/logical block size in guest is same as qemu
   parameters.

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
Acked-by: Feng Yang<fyang@redhat.com>
Acked-by: Yiqiao Pu <ypu@redhat.com>
Signed-off-by: Feng Yang <fyang@redhat.com>
config: Add unattended_install's RHEL guest side config to check_block_size sub case.

Signed-off-by: Feng Yang <fyang@redhat.com>