…otstrapping

In Prod, we are seeing the bootstrapping nodes are blocking the
new push, and this PR disables the status reporting if the app
is still bootstrapping.
This feature is especially important for DaVinci apps, which are
using multiple large stores and bootstrapping from an empty state
can take a long time and it can delay the new push significantly.

1. Subscription won't return if there are still active current version bootstrapping
   to avoid serving stale current version.
2. Delete the heartbeat entry for the current instance if the instance is bootstrapping
   to avoid Controller mark the bootstrapping node as crashed, which can fail the
   new push jobs.

…at Controller can ignore the report