fix inverted logic in Server.is_up()

jupyterhub/orm.py

@@ -103,14 +103,13 @@ class Server(Base):
             socket.create_connection((self.ip or 'localhost', self.port))
         except socket.error as e:
             if e.errno == errno.ECONNREFUSED:
-                return True
+                return False
             else:
                 raise
         else:
             return True
 
 
-
 class Proxy(Base):
     """A configurable-http-proxy instance.