Problem:
The variables cannot be filtered by activity instance scope.

Steps to reproduce:

1. go to Cockpit
2. select a process instance with variables in different scopes
3. open variables tab
4. select an activity on the diagram to filter variables

Observed Behavior:
All variables are shown.

Expected Behavior:
The variables are filtered by selected activity.

Hint:

• There are different options to filter variables
  1. by selecting an activity on the diagram
  2. by opening on the right side the filter and select an activity instance
  3. by selecting a scope within the variable table
• The request to fetch variables is executed twice with different query parameters.
• The problem might be [1].

[1]: https://github.com/camunda/camunda-bpm-webapp/blob/9e7e04a321720e15833cf4697d7e15001354abb1/ui/cockpit/plugins/base/app/views/processInstance/variableInstancesTab.js#L64-L69