Hmm.. looked up the two virgo SHA-1: 936d1102558597 -> b5280261fea8

In between these two, there were two commits that affects `/var/run/rackspace-monitoring-agent.pid`, which are
https://github.com/racker/virgo/commit/6c5e36761f29b1f717ab7f24fbab4e6a646b3119#util/constants.lua
and then, 
https://github.com/racker/virgo/commit/62deb1c3d46edddd15da47f2ad25c3bc96b83593#util/constants.lua

I guess before the default PID file, it was written to some directory that normal has write permission to?