Do not wait auto start to finish in order to complete project opening

Fix https://github.com/GNS3/gns3-gui/issues/2074

gns3server/controller/project.py

@@ -675,7 +675,10 @@ class Project:
         self._loading = False
         # Should we start the nodes when project is open
         if self._auto_start:
-            yield from self.start_all()
+            # Start all in the background without waiting for completion
+            # we ignore errors because we want to let the user open
+            # their project and fix it
+            asyncio.async(self.start_all())
 
     @asyncio.coroutine
     def wait_loaded(self):