fix running script/rails in a certain case

when run with an absolute path, through a symlink, for
some reason this got included twice

Change-Id: I7d03f7276fbfdf4315fa37a59226ea7fbc9a1a26
Reviewed-on: https://gerrit.instructure.com/38843
Reviewed-by: Rob Orton <rob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>