Unit tests for active config change broadcast

Modifies statsd unit tests to also assert the active configs changed
broadcast is called at the right time with the right configs. One case
has one config with multiple activation signals, while the other has
multiple configs that are activated at the same time with one signal.

Test: this is the test
Change-Id: I6e1cd19a8a0a8dbf9745152d4ad4980854be0cbd