qemu: block: Add node-names to JSON backing storage strings
qemu: block: Add node-names to JSON backing storage strings

Format out the node-name if it was assigned for JSON-based storage
specification.

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