ceph.in: use os._exit when we don't shut down

ceph.in: use os._exit when we don't shut down

If we experience a timeout, we don't bother shutting down rados, because
it can't currently handle one thread blocked (or running) library init
at the same time that another thread calls rados_shutdown().  This
behavior was recently introduced by c8f353c50bcd2a30be9e3600dba91912b8cd0429

However, sys.exit() runs all kinds of shutdown work that will also
interfere with the running librados threads.

Fix by using os._exit instead of sys.exit.

Fixes: https://tracker.ceph.com/issues/44566
Signed-off-by: Sage Weil <sage@redhat.com>