Operate on a copy of headers
Operate on a copy of headers

Avoids mutating a global headers object, repeating the leak we were
trying to avoid in the first place.

dcos/dcos,kensipe/dcos,surdy/dcos,GoelDeepak/dcos,mesosphere-mergebot/dcos,mesosphere-mergebot/mergebot-test-dcos,GoelDeepak/dcos,GoelDeepak/dcos,dcos/dcos,mesosphere-mergebot/mergebot-test-dcos,mesosphere-mergebot/mergebot-test-dcos,dcos/dcos,mesosphere-mergebot/dcos,dcos/dcos,mesosphere-mergebot/dcos,kensipe/dcos,mesosphere-mergebot/mergebot-test-dcos,surdy/dcos,dcos/dcos,kensipe/dcos,GoelDeepak/dcos,kensipe/dcos,surdy/dcos,mesosphere-mergebot/dcos,surdy/dcos