xfstests: renumber existing btrfs tests to start with 1

Current numbering is inheried from the single testsuite series. There
are only 6 btrfs-specific tests and it makes more sense to start adding
new ones at a more natural place than 300-something. There's no overlap
with the old and new numbers and I hope there' will be no confusion when
referencing them.

Signed-off-by: David Sterba <dsterba@suse.cz>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Rich Johnston <rjohnston@sgi.com>

tests/btrfs/001.out

@@ -0,0 +1,40 @@
+QA output created by 001
+Creating file foo in root dir
+List root dir
+foo
+Creating snapshot of root dir
+Create a snapshot of 'SCRATCH_MNT' in 'SCRATCH_MNT/snap'
+List root dir after snapshot
+foo
+snap
+List snapshot dir
+foo
+List root dir after rm of foo
+snap
+List snapshot dir
+foo
+Create subvolume 'SCRATCH_MNT/subvol'
+Listing root dir
+snap
+subvol
+Listing subvol
+Creating file bar in subvol
+Setting subvol to the default
+List root dir which is now subvol
+bar
+Mounting sbuvolid=0 for the root dir
+List root dir
+snap
+subvol
+Setting the root dir as the default again
+List root dir
+snap
+subvol
+Listing subvolumes
+snap
+subvol
+Delete subvolume 'SCRATCH_MNT/snap'
+List root dir
+subvol
+List root dir
+subvol