DNodeServer now ends all DNode connections when close() is called.
DNodeServer now ends all DNode connections when close() is called.

Without doing this, test suite doesn't terminate since the connections
keep the event loop active.  This is a temporary solution - once we
implement browser#close(), the browsers will be responsible for closing
their own client connections.

brianmcd/cloudbrowser,brianmcd/cloudbrowser,bladepan/cloudbrowser,bladepan/cloudbrowser,brianmcd/cloudbrowser,bladepan/cloudbrowser