Compute API reference should describe pause and suspend operations

[Matt Riedemann]

The pause:

https://developer.openstack.org/api-ref/compute/#pause-server-pause-action

And suspend:

https://developer.openstack.org/api-ref/compute/#suspend-server-suspend-action

APIs just say they pause and suspend the server, which does not really tell the user anything about what the difference is between the APIs, why you'd want to use one over the other, etc. We should describe more there.

For the libvirt driver, this describes the suspend operation:

https://libvirt.org/sources/virshcmdref/html/sect-managedsave.html

and

https://wiki.libvirt.org/page/VM_lifecycle#States_that_a_guest_domain_can_be_in

"Saved - Similar to the paused state, but the domain state is stored to persistent storage. Again, the domain in this state can be restored and it does not notice that any time has passed."

And for pause with libvirt:

https://wiki.libvirt.org/page/VM_lifecycle#Pausing_a_guest_domain