Don't consider strings with variables to be static
Summary: This is related to T8049. Maybe I am misinterpreting what the evalStatic method is meant to do, but I don't think that evalStatic should work on strings which contain interpolated variables.
Test Plan: Unit tests.
Reviewers: #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D13031