Summary: Fix the format of the export. Due to unknown reason the changes done in the D14933499 was [reverted back](https://our.intern.facebook.com/intern/diff/D14933499/?src_number=80619316) on the same diff. Thus this diff fixes the format of the metrics export Reviewed By: passy Differential Revision: D15239653 fbshipit-source-id: b9416f89e1b0022000d6201eb08ca1f456d5ed2e