shutdown upon parentchain UpdateAuthorized

[brenzi]

As an enhancement upon #1634, we could shut down already upon System.UpdateAuthorized and refuse to start the worker again until CodeUpdated

this may cause unnecessary downtime. For consideration

A better solution is #1257 which is tolerant against extrinsic failures

[clangenb]

This can cause significant downtime, no one knows when an authorized code will be enacted, as it even needs an extra extrinsic to enact it.