Description of problem:
Remove operations which are  NOT intended for direct usage from GUI

Version-Release number of selected component (if applicable):
jon 3.2 er7

How reproducible:
always

Steps to Reproduce:
1. Navigate to Storage node -> operations -> Schedules
2. 
3.

Actual results:
operations with are NOT intended for direct usage (decommision, add n maintenance, announce, prepare for bootstrap, etc..) are visible -> http://d.pr/i/kpPk  

Expected results:
operations with are NOT intended for direct usage (decommision, add n maintenance, announce, prepare for bootstrap, etc..) are not visible/accessible -> http://d.pr/i/kpPk 

Additional info:
having operations that should not scheduled confuses
if customer runs those operations - storage node gets into non-stable state and cannot be rolled back or fixed anymore