btrfs: update some tests to be able to run with btrfs-progs v6.11

btrfs: update some tests to be able to run with btrfs-progs v6.11

In btrfs-progs v6.11 the output of the "filesystem show" command changed
so that it no longers prints blank lines. This happened with commit
4331bfb011bd ("btrfs-progs: fi show: remove stray newline in filesystem
show").

We have some tests that expect the blank lines in their golden output,
and therefore they fail with btrfs-progs v6.11.

So update the filter _filter_btrfs_filesystem_show to remove blank lines
and change the golden output of the tests to not expect the blank lines,
making the tests work with btrfs-progs v6.11 and older versions.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>