Fix overriding of config from env vars.
Fix overriding of config from env vars.

ecbtln/mongo-web-shell,10gen-labs/mongo-web-shell,lnickers2004/mongo-web-shell,lnickers2004/mongo-web-shell,mongodb-labs/mongo-web-shell,lnickers2004/mongo-web-shell,lnickers2004/mongo-web-shell,ecbtln/mongo-web-shell,mongodb-labs/mongo-web-shell,mongodb-labs/mongo-web-shell,10gen-labs/mongo-web-shell,ecbtln/mongo-web-shell,pilliq/mongo-web-shell,pilliq/mongo-web-shell,pilliq/mongo-web-shell,10gen-labs/mongo-web-shell