qemu-iotests/063: Fix leaked image

qemu-iotests 063 left t.raw.raw1 behind in the scratch directory because
it used the wrong suffix. Make sure to clean it up after completing the
test.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
