/distribution/beaker/dogfood: also submit server-debug.log

Most interesting stack traces go into server-debug.log and not
server-errors.log, since CherryPy (frustratingly) logs exceptions in
request handling at the INFO level.

Change-Id: I73595dfca729ddae0dc7e487b52df7fd2bf1bde6
Merge "/distribution/beaker/dogfood: also submit server-debug.log" into develop