Just like with live-migration, custom CPU models might change after a
snapshot has been taken (or a VM suspended), which would lead to a
different QEMU invocation on rollback/resume.
Save the "-cpu" argument as a new "runningcpu" option into the VM conf
akin to "runningmachine" and use as override during rollback/resume.
No functional change with non-custom CPU types intended.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>