Comment 1 for bug 1421283

On primary mongo node config /etc/mongodb.conf doesn't contain parameter 'replset'. That's why you can see { "ok" : 0, "errmsg" : "server is not running with --replSet" } on error log. This parameter should be set if we are using more than one mongo node.
It should be passed from https://github.com/stackforge/fuel-library/blob/master/deployment/puppet/osnailyfacter/modular/mongo_primary.pp for primary node and from https://github.com/stackforge/fuel-library/blob/master/deployment/puppet/osnailyfacter/modular/mongo.pp for all secondary nodes.