block: Fix update of BDRV_O_AUTO_RDONLY in update_flags_from_options() Commit e35bdc123a4ace9f4d3fcca added the auto-read-only option and the code to update its corresponding flag in update_flags_from_options(), but forgot to clear the flag if auto-read-only is false. Signed-off-by: Alberto Garcia <berto@igalia.com> Reported-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>