Unset cloud provider if it gets uninstalled

We need to unset the current cloud provider when it gets uninstalled so
that we don't assume it is still there in subsequente calls.

Bug: 224800267
Test: atest PickerSyncControllerTest && Manual
Change-Id: I8075b47c49a1962398c4a9ccd1d7390c907e171f
3 files changed