Add configuration support for target latency

Configuration support for target latency value.

Tested live and checked using logs that correct values have gone to the LoadMonitor class.

Also tested error path on Sprout
As discussed, this error will be swallowed by `start-stop-daemon` (unlike the one in Sprout).  The latest Homestead fixes this to work like Sprout does, and we should make the same change here before pulling to Project Clearwater.