Do not add starting window after the starting data was cleared.

After moving the starting window logic to Shell, some timeing could be
changed. For some case the starting window could be added back to
window manager after app has drawn, for this case the mStartingData
was already cleared.
A reasonable solution should to prevent the starting window add back
to window manager if window manager already clear the starting data,
and for this case we don't need to remove the starting window from
window manager.

Bug: 182749276
Test: atest ActivityRecordTests
Change-Id: Iec8581908a413a1d8f70a2006d58386c5c8f5b86