btrfs-progs: qgroup create/destroy: fix argument parsing

btrfs-progs: qgroup create/destroy: fix argument parsing

"qgroup create/destroy" don't work from the following commit.

commit 176aeca9a148 ("btrfs-progs: add getopt stubs where needed")

* actual result

   ==================================================
   # ./btrfs qgroup create 1 /btrfs/sub
   btrfs qgroup create: too few arguments
   usage: btrfs qgroup create <qgroupid> <path>

       Create a subvolume quota group.
   ==================================================
   # btrfs qgroup create 1 /btrfs/sub
   # ./btrfs qgroup destroy 1 /btrfs/sub
   btrfs qgroup destroy: too few arguments
   usage: btrfs qgroup destroy <qgroupid> <path>

       Destroy a quota group.

   ==================================================

* expected result

   ==================================================
   # btrfs qgroup create 1 /btrfs/sub
   # btrfs qgroup destroy 1 /btrfs/sub/
   ==================================================

Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>