Fix bug when running "mixminion unittests" with umask 077
Fix bug when running "mixminion unittests" with umask 077

nmathewson/mixminion,mixminion/mixminion,rxcomm/mixminion,Javex/mixminion,nmathewson/mixminion,Javex/mixminion,reezer/mixminion,crooks/mixminion,nmathewson/mixminion,rxcomm/mixminion,rxcomm/mixminion,reezer/mixminion,nmathewson/mixminion,mixminion/mixminion,mixminion/mixminion,crooks/mixminion,mixminion/mixminion,crooks/mixminion,reezer/mixminion,crooks/mixminion,Javex/mixminion,Javex/mixminion,reezer/mixminion,rxcomm/mixminion