First kill detached providers, because of two reasons: - after killing all attached providers, all providers are then detached   and operation is repeated for those who were attached, - we don't want to remove keys for read-only attached providers, we only   want to detach them.
First kill detached providers, because of two reasons:
- after killing all attached providers, all providers are then detached
  and operation is repeated for those who were attached,
- we don't want to remove keys for read-only attached providers, we only
  want to detach them.

MFC after:	1 week

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