iotests: blacklist bochs and cloop for 205 and 208

Blacklist these formats, as they don't support image creation, as they
say:
    > ./qemu-img create -f bochs x 1m
    qemu-img: x: Format driver 'bochs' does not support image creation

    > ./qemu-img create -f cloop x 1m
    qemu-img: x: Format driver 'cloop' does not support image creation
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/205

@@ -153,4 +153,4 @@ class TestNbdServerRemove(iotests.QMPTestCase):
 
 
 if __name__ == '__main__':
-    iotests.main()
+    iotests.main(supported_fmts=['generic'])

tests/qemu-iotests/208

@@ -22,6 +22,8 @@
 
 import iotests
 
+iotests.verify_image_format(supported_fmts=['generic'])
+
 with iotests.FilePath('disk.img') as disk_img_path, \
      iotests.FilePath('disk-snapshot.img') as disk_snapshot_img_path, \
      iotests.FilePath('nbd.sock') as nbd_sock_path, \