Fix double counting issue for request metrics on timeout.
Fix double counting issue for request metrics on timeout.

Currently we record request metrics during the normal request flow and
we also manually invoke `Record` in the timeout handler to record
timeouts. This means that we effectively double count whenever we
timeout. This PR renames the `Record` function to `RecordRequestError`
to more accurately reflect the intended side-effect of the function
call.

Change-Id: Ie37fd0c1e501bd525640a434433d364a5fd6dde2

Kubernetes-commit: 4c6e7247878477a1f2efc26df7f141258010374f

kubernetes/kube-aggregator,kubernetes/kube-aggregator