ceph-volume: fix drive-group issue

The drive-group expects the batch_args to be a string,
however in the current version it is passed as a list
of one element, thus calling the first item of the list solves the issue.

Fixes: https://tracker.ceph.com/issues/59203

Signed-off-by: Mohan Sharma <mohan7427@gmail.com>

src/ceph-volume/ceph_volume/drive_group/main.py

@@ -78,7 +78,7 @@ def main(self):
             print(cmd)
         else:
             logger.info('Running ceph-volume command: {}'.format(cmd))
-            batch_args = cmd.split(' ')[2:]
+            batch_args = cmd[0].split(' ')[2:]
             b = Batch(batch_args)
             b.main()