Try to opportunistically flush statsd data in maintenance scripts

Try to opportunistically flush statsd data in maintenance scripts

This helps to avoid OOMs from buffer build-ups in the statsd
factory object. This piggy-backs on to the same checks used
for deferred update runs. In addition, the output() method
checks if the data size is getting large and emits if needed.

Bug: T181385
Change-Id: I598be98a5770f8358975815e51380c4b8f63a79e