[ironic] Retirement of VirtualPDU

Hi all, As it's clear the SNMP code in Ironic will be removed next cycle, and CI has been removed as well, we also will be needing to retire VirtualPDU as well -- either this cycle or next. VirtualPDU was never shipped for production use and only mapped SNMP calls into libvirt power actions for devstack. With these jobs removed, it no longer serves a purpose. Please speak up now if you oppose this retirement. Thanks! -- Jay Faulkner Open Source Developer G-Research OSS