Mock WifiPickerTracker.class for Roboletric test-cases

Bug: 214938188
Test: manual test
make RunSettingsRoboTests ROBOTEST_FILTER=NetworkRequestDialogActivityTest
make RunSettingsRoboTests ROBOTEST_FILTER=NetworkRequestDialogFragmentTest
make RunSettingsRoboTests ROBOTEST_FILTER=NetworkRequestErrorDialogFragmentTest
make RunSettingsRoboTests ROBOTEST_FILTER=WifiConnectionPreferenceControllerTest

Change-Id: I4c15c2a095203338bb9cf7bcd359242d59bf8b4e
4 files changed