[RHEL5.6] KVM: guest recognizes already detached disk

Issue

• If some disks are online attached/detached to a RHEL5.x guest OS before the guest OS loads acpiphp.ko module, the guest OS recognizes those already detached disks at the next online disk attachment time.
• Such (ghost) disks can't be detached from the guest OS until power off the guest OS. (Reboot doesn't work.)