remove lxml requirement
remove lxml requirement

this does not appear to be used anywhere in the code base, and is
probably vestigial from the nova split which needs it for libvirt xml
xpath.

Change-Id: If3a9acea16980ffaeb585fa3cffa053fa4b11f5d

dims/ironic,bacaldwell/ironic,openstack/ironic,openstack/ironic,SauloAislan/ironic,hpproliant/ironic,devananda/ironic,pshchelo/ironic,dims/ironic,bacaldwell/ironic,NaohiroTamura/ironic,ionutbalutoiu/ironic,ionutbalutoiu/ironic,NaohiroTamura/ironic,pshchelo/ironic,SauloAislan/ironic