🐛 Ensure returned informers are always correctly synced

[nvachhar]

specificInformersMap.Get may accidentally return an unsynced Informer (contained in the returned MapEntry). The condition occurs when 2 callers concurrently call Get for the same GVK after the specificInformersMap has been started. The first won't find the GVK in the cache. It will add it and wait for the informer to sync. The second will find it in the cache and erroneously return it before it syncs.This patch guarantees that all returned informers are synced by checking before return.

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[nvachhar]

/assign @DirectXMan12

[nvachhar]

Fixes #370

[nvachhar]

I'm working on the contributor agreement. Stay tuned. We had previously signed with Google before things moved over to CNCF, so I just have to get a new signature.

[nvachhar]

CNCF agreement is now signed. Should be ready for review.

[nvachhar]

Changed my github primary email. Maybe that'll help...

[nvachhar]

One more try. Logged into CNCF with github...

[DirectXMan12]

I think this tackles the case we care about satisfactorily. There's a bit of pseudo-UB if you fetch an informer while you're starting the cache, though.

[DirectXMan12]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: DirectXMan12, nvachhar

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[nvachhar]

A quick question for future contributions. What is pseudo-UB? I racked my brain trying to figure it out, but came up short...