Description of problem:
Refresh button in system tree menu is not working correctly, when adding/removing cluster when system tree is expanded after clicking the refresh button, system tree is not refreshed but stays in expanded version without update

Version-Release number of selected component (if applicable):
si 15.1

How reproducible:
90% of times

Steps to Reproduce:
1. Expand system tree
2. Add new/remove cluster from clusters tab
3. hit refresh button in the system tree tab
  
Actual results:
system tree is not updated by refresh button

Expected results:
System tree should collapsed and with next expand should show new updated system tree or just stay expanded and update itself

Additional info:
When this bug occures system tree can be updated only by collapsing it and expanding back again manually...