Ability to clear "Auto power on" flag for DR-ed VM

[randadinata]

Context

• XO version: XO appliance / stable branch / next-release branch

If from the sources:

• Component: xo-web (5.6.3) / xo-server (5.6.4)/ unknown
• Node/4.1.2: just execute npm version

Expected behavior

VM has "Auto power on" properties copied to DR host

Current behavior

This behaviour is expected. But, it would nice if we can have flag on DR dan CR job to clear the "Auto power on" flag on copied VMs to prevent accidental startup.

[olivierlambert]

Okay so to avoid adding more and more options everywhere, we chose to to thing differently: we'll block VM.start, so even if we copy the "Auto Power On" is copied, there's not risk it will be boot automatically.

When you'll try to boot it manually, it will display a message to force it if needed.