attempt a fix of userdata_update.q failure; look for binary data in the JSON and avoid it

Summary:
I indentified the error in the Hive logs, and confirmed the line in the file
causing problems has weird values in the nickname field.

Test Plan:
I ran the bad line through this program locally, and it successfully parses
on the second attempt.

Reviewers: eliana

Reviewed By: eliana

Differential Revision: http://phabricator.khanacademy.org/D2286