Perform the rounding to match a CHS geometry only in the legacy code
path in .bdrv_co_create_opts. QMP now requires that the user already
passes a CHS aligned image size, unless force-size=true is given.

CHS alignment is required to make the image compatible with Virtual PC,
but not for use with newer Microsoft hypervisors.

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