snapshots: Use --quiesce and --live during creation as appropriate

[mvollmer]

This is the recommended way to create snapshots of running machines.

[mvollmer]

I guess we should not use --live unless we also give people the option to use disk-only snapshots for running machines. --live seems to be risky in that it might require lots of unexpected storage amounts.

[mvollmer]

For my own record:

--quiesce requires --disk-only --memspec conflicts with --disk-only --quiesce causes the snapshot creation to fail when there is no agent in the gues --quiesce with a stopped machine does nothing

Thus: quiesce can only be used for disk only snapshots of running machines, and it might cause the snapshot creation to fail in that case. Do we need to find a way to figure out whether the guest has an agent?

[mvollmer]

For my own record:

--quiesce requires --disk-only --memspec conflicts with --disk-only --quiesce causes the snapshot creation to fail when there is no agent in the gues --quiesce with a stopped machine does nothing

Thus: quiesce can only be used for disk only snapshots of running machines, and it might cause the snapshot creation to fail in that case. Do we need to find a way to figure out whether the guest has an agent?

"Currently, there is no reliable method/API to tell if GA is running", https://wiki.libvirt.org/Qemu_guest_agent.html