[libvirt] [PATCH] OpenVZ xml refactoring

Patch switch OpenVZ XML format to generic. main changes: - I used generic virDomainNetDef to define network in container. And wrote function to apply virDomainNetDef for container. Method virDomainNetDefParseXML is public now. - tag "container" is changed to "devices" - changed format of tag "filesystem" - added processing "vcpu" tag.