qemu: migration: Properly setup mirror for blockdev configurations
qemu: migration: Properly setup mirror for blockdev configurations

With blockdev we need to refer to the nodename of the disk source image
as the source argument for the blockdev-mirror operation while still
keeping the old job name. With blockdev we must also persist the job in
qemu.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Eric Blake <a9da18479c871fe903d9590822cfe2629c6a4d11@redhat.com>

libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,olafhering/libvirt,zippy2/libvirt,olafhering/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,libvirt/libvirt,fabianfreyer/libvirt,zippy2/libvirt,jfehlig/libvirt,jfehlig/libvirt,crobinso/libvirt,crobinso/libvirt,crobinso/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,crobinso/libvirt,zippy2/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,nertpinx/libvirt,olafhering/libvirt,nertpinx/libvirt,olafhering/libvirt,jardasgit/libvirt,jardasgit/libvirt,libvirt/libvirt,jardasgit/libvirt,zippy2/libvirt,jfehlig/libvirt,libvirt/libvirt