Having the field set in modifyCommonNamespaceOptions is misleading,
since for the actual container it is later unconditionally overwritten
to point to the sandbox container.
So let's move its setting to modifyHostOptionsForSandbox (renamed from
modifyHostNetworkOptionForSandbox as it's not about network only), since
that reflects what actually happens in practice.
This commit is purely a refactor, it doesn't change any behavior.
Automatic merge from submit-queue (batch tested with PRs 49651, 49707, 49662, 47019, 49747)
Add support for `no_new_privs` via AllowPrivilegeEscalation
**What this PR does / why we need it**:
Implements kubernetes/community#639
Fixes#38417
Adds `AllowPrivilegeEscalation` and `DefaultAllowPrivilegeEscalation` to `PodSecurityPolicy`.
Adds `AllowPrivilegeEscalation` to container `SecurityContext`.
Adds the proposed behavior to `kuberuntime`, `dockershim`, and `rkt`. Adds a bunch of unit tests to ensure the desired default behavior and that when `DefaultAllowPrivilegeEscalation` is explicitly set.
Tests pass locally with docker and rkt runtimes. There are also a few integration tests with a `setuid` binary for sanity.
**Release note**:
```release-note
Adds AllowPrivilegeEscalation to control whether a process can gain more privileges than it's parent process
```
This change moves the code specific to docker to kubelet/dockertools,
while leaving the common utility functions at its current package
(pkg/securitycontext).
When we deprecate dockertools in the future, the code will be moved to
pkg/kubelet/dockershim instead.
