lei: restore default __DIE__ handler for event loop

lei: restore default __DIE__ handler for event loop

The kqueue code paths will trigger exceptions which are caught
by eval{}, so we can't be calling exit() from the __DIE__
handler and expect eval to catch it.

We only need the __DIE__ handler to deal with fork or open
failures at startup (since stderr is pointed to /dev/null).
After that we can rely on OnDestroy writing errors to syslog
when it goes out of scope.