Make watch back off from 5 second checking

[kemp-google]

Right now the pipelines too just polls for operation status every 5 seconds. This sort of interval doesn't really make sense for long running operations. We should have a scheme that backs off pretty quickly after events and resets the delay each time there is an event (so that events that finish quickly get noticed quickly).

For example, the initial state would be every 5 seconds with an exponential back off (up to, say 1 minute), then each event would restart the backoff progression.