Beego currently handles the case of "conf/app.conf"
not existing, but all other errors are not logged.
This fixes that.

I ran into an issue where beego was not listening on the
correct port, and it turned out that the conf/app.conf file
had a colon ":" instead of an equal sign "=" (confusion of
INI vs YAML formats).  When there was a parsing error, beego
would give up on parsing app.conf and not log anything to the
console.