[core] Outbounds should do an actual close when error instead of only…

… a state change

src/outbound.cpp

@@ -139,7 +139,7 @@ void Outbound::error(StreamEnd::Error err) {
   m_error = err;
   pjs::Ref<StreamEnd> eos(StreamEnd::make(err));
   input(eos);
-  state(State::closed);
+  close();
 }
 
 void Outbound::describe(char *buf, size_t len) {