This changes the Kubelet configuration flag precedence order so that
flags take precedence over config from files/ConfigMaps.
See #56171 for rationale.
Note: Feature gates accumulate with the following
precedence (greater number overrides lesser number):
1. file-based config
2. dynamic cofig
3. flag-based config
This explicitly registers Kubelet flags from libraries that were
registering flags globally, and stops parsing the global flag set.
In general, we should always be explicit about flags we register
and parse, so that we maintain control over our command-line API.
This avoids some conflict with the built-in `flag` module in Go. The
module was already being renamed to `verflag` on import anyways, so we
might as well just call it that.
Tested:
- hack/build-go.sh and ran the resulting binaries with -version args.
Signed-off-by: Filipe Brandenburger <filbranden@google.com>