btrfs/003: fix failure on new btrfs-progs versions

btrfs/003: fix failure on new btrfs-progs versions

Starting with btrfs-progs version 5.19, the output of 'filesystem show'
command changed when we have a missing device. The old output was like the
following:

    Label: none  uuid: 139ef309-021f-4b98-a3a8-ce230a83b1e2
            Total devices 2 FS bytes used 128.00KiB
            devid    1 size 5.00GiB used 1.26GiB path /dev/loop0
            *** Some devices missing

While the new output (btrfs-progs 5.19+) is like the following:

    Label: none  uuid: 4a85a40b-9b79-4bde-8e52-c65a550a176b
            Total devices 2 FS bytes used 128.00KiB
            devid    1 size 5.00GiB used 1.26GiB path /dev/loop0
            devid    2 size 0 used 0 path /dev/loop1 MISSING

More specifically it happened in the following btrfs-progs commit:

    957a79c9b016 ("btrfs-progs: fi show: print missing device for a mounted file system")

This is making btrfs/003 fail with btrfs-progs 5.19+. Update the grep
filter in btrfs/003 so that it works with both output formats.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>