Data/activation broadcasts use elapsed realtime

The data and activation broadcasts were guardrailed using
elapsedRealtime of the *LogEvent*. However, it's possible to use
incorrect timestamps, and it's also possible that we could process
events that are old, which would result in the broadcast getting sent
too frequently. To fix this, we should use the current elapsedRealtime
instead of the LogEvent's elapsedRealtime.

I can remove the config activation broadcast if we think we should hold
off on it.

Test: bit statsd_test:*
Bug: 143155387
Change-Id: I4c58d2558d6ba3b4fd15a4a619d6f80a7bd7113f