Description of problem:
When choosing vm in UP mode + vm in DOWN mode (or vm in UP mode + vm in SUSPENDED mode)
the reboot button is disabeld. 
according the thumb rule of multipule selstion, if at least one of
the VMs selected is in a status which permits the operation then it will
be allowed

Version-Release number of selected component (if applicable):
3.6
vdsm-4.17.0-632.git19a83a2.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1.Select vm in UP mode + vm in Down mode 
2.right cliclk -> see that the reboot button is disabeld
3.

Actual results:
Reboot button is disabeld

Expected results:
The reboot button is should be enabeld

Additional info: