qemu-io: Check for trailing chars Make sure there's not trailing garbage, e.g. "64k-whatever-i-want-here" Reported-by: Max Reitz <mreitz@redhat.com> Signed-off-by: John Snow <jsnow@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>