Don't record thread information from shutdown thread

If we are shutting down with no attached thread we re-attach the thread.
If re-attaching gets into some problems we unregister the thread again
which records the information about the thread again. So just ignore
updates from the Shutdown thread.

Bug: 279548114
Test: art/test.py -t 2246
Change-Id: I5357c0653e5006428f75b5449889495dfa7f543d
1 file changed