Description of problem:
When user tries to scan alignment, one after another we are getting a message on UI:
"Error while executing action:
ACTION_TYPE_FAILED_DISK_IS_USED_BY_GET_ALIGNMENT"


Version-Release number of selected component (if applicable):
Version-Release number of selected component (if applicable):
rhevm-3.3.0-0.28.beta1.el6ev.noarch
rhevm-webadmin-portal-3.3.0-0.28.beta1.el6ev.noarch

How reproducible:
50%

Steps to Reproduce:
1. Create a qcow disk (create a disk in a VM and then create a snapshot)
2. Right click on the disk and pick Scan Alignment
3. Right click on it again and pick Scan Alignment


Expected results:
The message should be presented in appropriate form. 

Additional info: