qcow2: CHECK_OFLAG_COPIED is obsolete

CHECK_OFLAG_COPIED as a parameter to check_refcounts_l1 and
check_refcounts_l2 is obselete now, since the OFLAG_COPIED consistency
check is actually no longer performed by these functions (but by
check_oflag_copied).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
