Put an app in standby, make it show a toast and ensure
that it doesn't come out of standby. This is to test
for a bug fix for the same behavior.
Bug: 31544592
Test: cts-tradefed run commandAndExit cts -m CtsHostsideNetworkTests -t com.android.cts.net.HostsideRestrictBackgroundNetworkTests#testAppIdle_toast
Change-Id: I796ecde8e346c308a27969d873e3ce384414fee3