Fix flake in testConnectivityDiagnosticsCallbackOnConnectivityReported

The test relied on waitForIdle to ensure diagnostics callbacks were called,
but as this may require several iterations in the handler queue, this makes
the test unreliable.

Use mockito timeouts on the verify() calls instead.

Bug: 192651465
Change-Id: Iae1704af7ae3649eae301c6aee223ac753629d55
Test: atest ConnectivityServiceTest
1 file changed