WifiConnectivityManagerTest: exponential backoff periodic scan

Add a couple of unit tests to cover the periodic scan exponential
backoff feature.

Extended MockAlarmManager class such that users can query a
pending alarm's trigger time.

Bug: 28750989
Change-Id: I9520477180786fce2937e5fa87f790f60f12a3da
3 files changed
tree: d7d3f00fdb6e4e29f5020d5c1b1e1b8e189e84db
  1. service/
  2. tests/