R1:e09d29fb1a3e

Clean up the workflow for some post-push logging code

Summary:
Ref T13216. When a repository is clustered, we run this cleanup code (to tell the repository to update, and log some timing information) on both nodes. Currently, we do slightly too much work, which is unnecessary and can be a bit confusing to human readers.

The double update message doesn't hurt anything, but there's no reason to write it twice.

Likewise, the second timing information update query doesn't do anything: there's no PushEvent…