Add error handling and other improvements to Bugreporting API

* Validate input arguments
* Ensure primary user
* Handle remote exceptions
* Pass error conditions to listener
* Ensure only one bugreport is in progress, at least via the API.

BUG: 123584708
BUG: 123571915
Test: Builds
Test: Manual; unit tests coming up

Change-Id: I4d1e0000fe815a02b82ce625864759fd818e6a24