Nodes appear to be offline
If the server reboots, the nodes status field is not set properly when using multiple workers. It seems likely that the `start()` method is triggered after some of the clients (=nodes) reconnected. 

Reported by @anjavangestel 
diff --git a/vantage6-server/vantage6/server/__init__.py b/vantage6-server/vantage6/server/__init__.py
index a525cd5c..65a305c6 100644
--- a/vantage6-server/vantage6/server/__init__.py
+++ b/vantage6-server/vantage6/server/__init__.py
@@ -78,6 +78,9 @@ class ServerApp:
         # Setup the Flask-Mail client
         self.mail = MailService(self.app, Mail(self.app))
 
+        # Set nodes to offline -- required before setting up the SocketIO
+        self._set_nodes_offline()
+
         # Setup websocket channel
         self.socketio = self.setup_socket_connection()
 
@@ -129,6 +132,14 @@ class ServerApp:
 
         return socketio
 
+    @staticmethod
+    def _set_nodes_offline():
+        """Set all nodes to offline (before starting the socket connection)."""
+        nodes = db.Node.get()
+        for node in nodes:
+            node.status = 'offline'
+            node.save()
+
     @staticmethod
     def configure_logging():
         """Turn 3rd party loggers off."""
@@ -407,14 +418,6 @@ class ServerApp:
                            password=SUPER_USER_INFO['password'])
             user.save()
 
-        # set all nodes to offline
-        # TODO: this is *not* the way
-        nodes = db.Node.get()
-        for node in nodes:
-            node.status = 'offline'
-            node.save()
-        # session.commit()
-
         return self
 
 
['vantage6-server/vantage6/server/__init__.py']