Extract general code from qemuDomainReAttachHostScsiDevices to
virHostdevDomainReAttachHostScsiDevices.

Extract general code from qemuDomainReAttachHostUsbDevices to
virHostdevDomainReAttachHostUsbDevices.

Extract general code from qemuPrepareHostSCSIDevices to
virHostdevPrepareHostSCSIDevices.

Extract general code from qemuPrepareHostUSBDevices to
virHostdevPrepareHostUSBDevices.

Extract general code from qemuUpdateActiveScsiHostdevs to
virHostdevUpdateActiveScsiHostdevs

Extract general code from qemuUpdateActiveUsbHostdevs to
virHostdevUpdateActiveUsbHostdevs.

Extract general code from qemuUpdateActivePciHostdevs to
virHostdevUpdateActivePciHostdevs.

Signed-off-by: NChunyan Liu <cyliu@suse.com>

Only wait for kvm device cleanup if the driver is pci-stub

Extract general code from qemuPrepareHostdevPCIDevices to
virHostdevPrepareHostdevPCIDevices.

For extracting hostdev codes from qemu_hostdev.c to common library, change qemu
specific COLD_BOOT handling to be a flag, and pass it to hostdev functions.

For extracting hostdev codes from qemu_hostdev.c to common library, change qemu
specific cfg->relaxedACS handling to be a flag, and pass it to hostdev
functions.

Same logic of preparing/reattaching hostdevs could be used in attach/detach
hotplug places, so reuse hostdev interfaces to avoid duplicate, also for later
extracting general code to common library.

Update parameters from vm->def to specific name, hostdevs, nhostdevs to keep
consistentcy with PreparePCIDevices and PrepareSCSIDevices. And, at the same
time, make it reusable in later patch.

Use virObject to virHostdevManager, so that each driver using virHostdevManager
can keep a reference to it, and through counting refs to make virHostdevManager
get freed.