Description of problem:
If a VM doesn't have guest agent, reboot button in webadmin is disabled.
Same VM can be rebooted from API.

Version-Release number of selected component (if applicable):
vt5

How reproducible:
always

Steps to Reproduce:
1. Create VM without guest agent
2. Go to webadmin and run VM
3. Look at reboot button in top menubar - it's disabled
4. Try to reboot from API - it works correctly

Actual results:
Reboot button is disabled in webadmin, while rebooting through API works

Expected results:
Reboot button should be enabled in webadmin

Additional info:
Latest vdsm for rhev 3.5 supports rebooting VM without guest agent, and UI is still checking if VM has guest agent running