Webapp should return an http response code != 200 on error

Even if the webapp encounters an error, it still returns "200" as return code.

--- git/bitmask ‹master* ⁇› » curl -k -s  https://dev.bitmask.net |grep -i ouch

Ouch!

--- git/bitmask ‹master* ⁇› » curl -k -s -o /dev/null -w "%{http_code}" https://dev.bitmask.net
200%                                                                                                   

"leap test" tests if the webapp is up and running, and the test falsly succeeds because of this.

(from redmine: created on 2014-10-06, closed on 2014-11-12)