btrfs/025: make test more robust

btrfs/025: make test more robust

Make the test btrfs/025 not depend on the output of the btrfs tools
subvolume, send, receive and filesystem commands output. The output
of these commands has changed several times in the past, and it can
change again in the future. Therefore just test for failure/success
and not for the exact output on the success case.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>