xfstests: wipefs new device in btrfs/003

xfstests: wipefs new device in btrfs/003

We changed btrfs device add to check and see if there is an existing fs on the
device we are adding, so you now have to do -f if you want to do this.  In order
to get around checking to see if we have this version of btrfs-progs just wipefs
the device we're adding to make sure the device add will pass no matter which
version of btrfs-progs you have.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Rich Johnston <rjohnston@sgi.com>