--maxrss: force exit if reactor.stop doesn't work.
--maxrss: force exit if reactor.stop doesn't work.

This makes --maxrss work for me in qt5. Without the fix
process never exits when max RSS is exceeded, and
further RSS checks print ReactorNotRunning exceptions.
See also: https://github.com/scrapinghub/splash/pull/96.

pombredanne/splash,Youwotma/splash,pombredanne/splash,pawelmhm/splash,pombredanne/splash,Youwotma/splash,Youwotma/splash,pawelmhm/splash,pawelmhm/splash