Adding error counters for statd clients

[kwoodson]

Adding statsd clients for cosmos, k8s, and azure client libraries.

Fixes #130

[jim-minter]

@mjudeikis convinced me that this function was OK back in the day but I am still doubtful about it.

If t.tr.RoundTrip(req) returns an error, then the defer() runs, then ru, err = strconv.ParseFloat(requestCharge, 64) runs successfully, does that mean that the original error gets overwritten and the end user never sees it?

I think we might need to use a different variable name from err throughout the defer() - and here we need to test the original error to decide whether to increment client.cosmosdb.errors or not.

@kwoodson please can you investigate / fix as part of this PR?

[kwoodson]

@jim-minter @mjudeikis I have renamed the err variable inside of the defer and then I have setup the tests to verify the emits are being called.

Is this more in line with what you wanted?

[mjudeikis]

Im a little bit confused about the code bellow (might be lack of coffee).
I think readability of this function is terrible (my fault).
Maybe we should not do empty return with return t.tr.RoundTrip(req)

and do something like :

defer(){
// RU cound parsing and checking
}
resp, err:= RoundTrip(req)
if err!=nil{
// emit CosmosDB error metric
}
return resp, err

As now this empty return and enourmous defer is confusing a lot!

[kwoodson]

Updated to fix import groups in test file.

[kwoodson]

Failing on the assert library. Will update.

	imports github.com/stretchr/testify/assert: cannot find package "github.com/stretchr/testify/assert" in any of:

[nilsanderselde]

Typo

[kwoodson]

@mjudeikis @jim-minter PTAL, thanks.

[jim-minter]

some notes - let's discuss the tricky defer bit on a call.

[jim-minter]

preferred for consistency with the rest of the codebase:

controller := gomock.NewController(t)
defer controller.Finish()

(throughout PR)