Fix some straggling qsprintf() warnings in repository import

Summary:
Ref T13217. See https://discourse.phabricator-community.org/t/unsafe-raw-string-warnings-while-importing-git-commits/2191.

Hunt down and fix two more qsprintf() things.

I just converted the "performance optimization" into a normal, safe call since we're dealing with far less SVN stuff nowadays and the actual issue has been lost in the mists of time. If it resurfaces, we can take another look.

Test Plan: Imported some commits, no longer saw these warnings in the daemon logs.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13217

Differential Revision: https://secure.phabricator.com/D19869