Rerun causes memory leak if enabled on KELO NUC

[m-decoster]

We left the python test_server.py script running during lunch today and when we came back, the KELO NUC became unresponsive (very slow and not accepting new SSH connections).

[m-decoster]

This appears to be a memory leak: memory keeps increasing while the server is running but idle.

[m-decoster]

Profiling shows that the leak comes from rerun. It is not clear why exactly rerun is causing large memory usage, because the process is set to use a maximum of 1GB (and it mentions dropping old messages). Rerun logging has been set to disabled by default in d6ba06c until we find the cause.

To profile:

Add @profile above def step() in robile_platform.py, and then run

python -m memory_profiler test_server.py