Don't send onMultiWindowModeChanged if relaunch activity.

If an activity is going to do relaunch, send onMultiWindowModeChanged
sounds meaningless since the activity will be destroy and re-create.
To narrow down the scope, this API should only be useful if the
activity want to handle onConfigurationChanged.

Bug: 162473704
Test: atest ActivityLifecyclePipTests ActivityLifecycleSplitScreenTests
ActivityLifecycleTopResumedStateTests PinnedStackTests SplitScreenTests
ActivityLifecycleKeyguardTests

Change-Id: If4e672e5a891ac315ecc6783af764dfc20ebfeb9