I converted this call incorrectly in D16092. We should pass the PhutilURI object, not the string version of it.
Specifically, this resulted in hitting an error like this if a replica needed synchronization:
[2016-08-11 21:22:37] EXCEPTION: (InvalidArgumentException) Argument 1 passed to DiffusionCommandEngine::setURI() must be an instance of PhutilURI, string given, called in... #0 PhutilErrorHandler::handleError(integer, string, string, integer, array) called at [<phabricator>/src/applications/diffusion/protocol/DiffusionCommandEngine.php:52] #1 DiffusionCommandEngine::setURI(string) called at [<phabricator>/src/applications/diffusion/protocol/DiffusionRepositoryClusterEngine.php:601] ...