Fix yank on multifd + postcopy

Leonardo Brásrequested to merge
LeoBras/centos-qemu-kvm:pc_mfd_c9s into c9s

Merge Request Required Information

Summary of Changes

Make sure to always yank unregister multifd channels before unregistering the yank instance. Some other code improvements. 1 requirement patches: improving multi-channel checks.

Approved Bugzilla Ticket

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=2106726

All submissions to CentOS Stream must reference an approved ticket in Red Hat Bugzilla. Please follow the CentOS Stream contribution documentation for how to file this ticket and have it approved.

Edited by Leonardo Brás

Merge request reports