Close mDragState immediately when error

Previously if we encounter an error at performDrag, it sometimes just
returns and lets MSG_DRAG_START_TIMEOUT clean up the drag state.

It means users cannot start another drag and drop operation before
timeout.

The CL fix the error handling so that it immediately cleans the drag
state on errors.

Bug: 69141835
Test: android.server.wm.CrossAppDragAndDropTests, manually check the
      drag and drop behavior on test app.
Change-Id: Ibc5784a842eed77e2fa082d8f38d69acc9954e3e