Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
change deprecated Kubelet --allow-privileged flag default to true
This enables a smooth transition to PSP. Today, users would have to
manually set --allow-privileged to true before transitioning to PSP,
which isn't a smooth deprecation path for the flag (we want people
to *stop* setting it). This PR makes the default behavior isomorphic
with what will happen after the flag is removed.
Defaulting --allow-privileged to true should be safe, because it simply
allows a superset of Pods to run (all workloads continue to work).
WRT https://github.com/kubernetes/kubernetes/issues/58010#issuecomment-383264473
the --allow-privileged flag is effectively useless for security, so this
shouldn't be a concern from that perspective.
I also bumped the deprecation timeline in the comment to 1.13.0, so that
we give people the full period of time to stop setting
--allow-privileged, now that the behavior makes it possible to do so.
```release-note
The Kubelet's deprecated --allow-privileged flag now defaults to true. This enables users to stop setting --allow-privileged in order to transition to PodSecurityPolicy. Previously, users had to continue setting --allow-privileged, because the default was false.
```
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