btrfs-progs: inspect subvolid-resolve: fix argument parsing

btrfs-progs: inspect subvolid-resolve: fix argument parsing

"inspect-internal subvolid-resolve" doesn't work from the following commit.

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

It's because 1st argument, subvolid, is also used for the pathname of
filesystem. 2nd argument should be used for this purpose instead.

* actual result

   ==================================================
   # ./btrfs inspect-internal subvolid-resolve 260 /btrfs
   ERROR: cannot access '260': No such file or directory
   ==================================================

* expected result

   ==================================================
   # btrfs inspect-internal subvolid-resolve 260 /btrfs
   snap
   ==================================================

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