Clear AppTransition.mOverrideTaskTransition.

Once AppTransition.mOverrideTaskTransition is set, we never reset it.
Should be reset in AppTransition#clear call.

Test: atest ActivityTransitionTests
Bug: 170251468
Change-Id: I9fe9d24598df10aaaa6cca724ed2beb5ed8b3785

services/core/java/com/android/server/wm/AppTransition.java

@@ -474,6 +474,7 @@ public class AppTransition implements Dump {
         mNextAppTransitionAnimationsSpecsFuture = null;
         mDefaultNextAppTransitionAnimationSpec = null;
         mAnimationFinishedCallback = null;
+        mOverrideTaskTransition = false;
         mNextAppTransitionIsSync = false;
     }