Improve the caching transport tests

The caching transport tests can fail when running the device tests if the simulator looses network connectivity. This PR changes the test to use a `FakeReliableNetworkStatusListener ` implementation of `INetworkStatusListener` that ignores the real network status and just pretends that everything is OK, so that test reliability isn't impacted by network connectivity.

Extracted from #4294

#skip-changelog

Author: jamescrosswell