This reverts commit 5279b303.

We no longer need this check because exact=true forces the block driver
to give the image the exact size requested by the user.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190918095144.955-9-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>