Add status code label to server latency histogram

[ashamukov]

Hi Dino! Eventually made a PR for #50 :)
@dinowernli

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[ashamukov]

@googlebot I signed it!

[dinowernli]

Thanks for your contribution! This is generally looking nice, just a few small suggestions here and there.

[dinowernli]

Looking great, almost there.

[dinowernli]

LGTM, thanks for the contribution.

[ashamukov]

Thanks a lot for your help!