Work around OSX after Yosemite no longer respecting CURLOPT_CAINFO

Summary: Fixes T5913. See discussion in that task.

Test Plan: Will make affected users in T5913 test.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: ide, epriestley

Maniphest Tasks: T5913

Differential Revision: https://secure.phabricator.com/D10315