Add validateK8sApi flag

[Mmduh-483]

When this flag is set it validates that multus can communicate with Kubernetes API and if failed to communicate it fails the cni. If set to false then skip failure when multus can't get pod data

[coveralls]

Pull Request Test Coverage Report for Build 565848041

• 2 of 16 (12.5%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.4%) to 70.446%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/multus/multus.go	2	16	12.5%

Totals
Change from base Build 552451364:	-0.4%
Covered Lines:	1137
Relevant Lines:	1614

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💛 - Coveralls

[dougbtv]

We decided we'll move forward, but with making this behavior configurable.

• types, and conf.go -- have the structures and parsing for config options
• docs/configuration.md -- which should be updated to describe the flag

[Mmduh-483]

@dougbtv

[s1061123]

Why default is false?

[s1061123]

Thank you so much for update PR, first.

multi-net-spec of NPWG defines that the plugin need to communicate to Kubernetes API and if cannot make it, plguin should cancel to create pod as error (see section 7.2 for details). So if we change 'skip api' is false as default, multus-cni does not following the multi-net-spec of NPWG.

I hope that multus-cni should following spec because multus-cni is the reference implementation of multi-net-spec of NPWG.

So the option should be opt-in configuration as following:

• option name could be ignoreK8sAPI(in json) / --ignore-k8s-api (in shell script) or something like that
• default behavior keeps as it is, 'fail (i.e. cancel to create pod) if multus cannot communicate k8s api' as spec mentioned

[dougbtv]

Yeah, let's flip that logic so the default matches the spec. And I also like the name ignoreK8sAPI.

If this is a problem, we could also bring it back up at the NPWG.

[Mmduh-483]

@s1061123 @dougbtv Thanks for your comments, after internal discussion we decided to go with another approach to handle the network operator use case