virDomainHugepagesFormat: Use virXMLFormatElementEmpty
virDomainHugepagesFormat: Use virXMLFormatElementEmpty

Refactor the function to use modern XML formatting machinery.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Tested-by: Rohit Kumar <380c8fbe843a355da9c7be37fa042183ef2c7b81@nutanix.com>

libvirt/libvirt,zippy2/libvirt,libvirt/libvirt,crobinso/libvirt,zippy2/libvirt,olafhering/libvirt,libvirt/libvirt,zippy2/libvirt,crobinso/libvirt,jfehlig/libvirt,olafhering/libvirt,libvirt/libvirt,jfehlig/libvirt,olafhering/libvirt,crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt,crobinso/libvirt,jfehlig/libvirt,olafhering/libvirt