Export namespace in ArcanistUnitTestResult dictionary

Summary: D7952 added namespaces to ArcanistUnitTestResult but these are not exported and thus don't get sent from client to server.

Test Plan: Uploaded a diff and inspected the contents of the phabricator_differential.differential_diffproperty table.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11208