Make View#isTemporarilyDetached() less confusing

In Android N, View#isTemporarilyDetached() returns true if it is called
when the same View instance is handling View#onFinishTemporaryDetach().

Returning true there is, however, sometimes confusing, especially
scenarios like the following case:

    @Override
    public void onFinishTemporaryDetach() {
        doSomeRestoringWorks();
    }

    private void doSomeRestoringWorks() {
        doSomething();
    }

    private doSomething() {
        if (isTemporarilyDetached()) {
            // As of N, we hit here if this is called as a result of
            // View#onFinishTemporaryDetach().
        } else {
            // but is the logic here is more likely to be appropriate
            // when handling View#onFinishTemporaryDetach()?
        }
    }

What this CL aims to do is to let View#isTemporarilyDetached() return
false when it is called while handling View#onFinishTemporaryDetach(),
because it should make View#onFinishTemporaryDetach() more useful.

Regarding the app compatibility, View#isTemporarilyDetached() was added
in API 24 hence the impact on this change is still limited.

Bug: 30791718
Change-Id: If384da9f9e6ff849598896901626fd021bae5cda