Fix specifying problem type in local mode

Test Plan:
Hit a bunch of problem types directly in local mode and verify the correct problem type was shown:
http://exercises.ka.local/exercises/age_word_problems.html?debug&problem=solve-older-1
http://exercises.ka.local/exercises/age_word_problems.html?debug&problem=solve-older-3
http://exercises.ka.local/exercises/age_word_problems.html?debug&problem=0
http://exercises.ka.local/exercises/age_word_problems.html?debug&problem=3

Auditors: brianmerlob