The pointer to the qemu driver is already included in domain object's
private data, so does not need to be passed as yet another parameter
when the domain object is already passed.

Also removes parameter 'driver' from functions which had it just because of
qemuBlockJobUpdate.
Signed-off-by: NRoland Schulz <schullzroll@gmail.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NJán Tomko <jtomko@redhat.com>