Update cpu_hotplug.md

[saurabhsadhalesuse]

What this PR does / why we need it:

The documentation incorrectly describes the previous behaviour of vCPU hot plug.

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[aburdenthehand]

Suggested change

	Before CPU hotplug was introduced, the VM owner could not change these integers in the VM template while the VM is running, and they were staged until the next boot cycle. With CPU hotplug, it is possible to patch the `sockets` integer in the VM template and the change will take effect right away.
	Before CPU hotplug was introduced, the VM owner could change these integers in the VM template while the VM was running but they would not take effect in the running VM until the next boot cycle. With CPU hotplug, it is possible to patch the `sockets` integer in the VM template and the change will take effect right away.

I don't think the original sentence is incorrect but I completely agree that it is not clear in it's current state.
What it is saying is that before the CPU hotplug feature, you could update the VM config but there would be no immediate change to the VMI (running VM): you had to reboot the VM before those changes would take place.
@iholder101 Can you please take a quick look to confirm?

[iholder101]

I don't think the original sentence is incorrect but I completely agree that it is not clear in it's current state. What it is saying is that before the CPU hotplug feature, you could update the VM config but there would be no immediate change to the VMI (running VM): you had to reboot the VM before those changes would take place.
@iholder101 Can you please take a quick look to confirm?

Yes, that's entirely correct.

However, TBH I think that the original sentence was the best phrasing IMO. I think "but they would not be staged" is also misleading here, as in this context the meaning of a "staged change" is that it is changed on the VM yaml, but hadn't affected the VMI yet (but will make an effect on the next reboot).

Maybe the "staged change" terminology is misleading altogether?

[aburdenthehand]

Thanks @iholder101
I did not know that about the term 'staged change' :)
I've updated the suggested text to just use 'take effect in the running VM', which echoes the following sentence as well.