StatsdStats: improve activation time logging

Add logging to record whenever the 10 second guardrail for sending
active configs changed broadcast is met, so that we know when the
broadcast would not have been sent.
Add activation time for configs that are active when the device boots.
This will help determine whether or not statsd thinks configs are active
and will help debug issues like b/133809948

Bug: 133809948
Test: bit statsd_test:*
Test: manually rebooted to make sure activation time was logged
Change-Id: Ifa72202bc52485e4953e49d78dffea685cc3d1e7