* src/util/xml.c: The virXPath... function take extra care to preserve
the XPath context node (ctxt->node) but in the case of virXPathString
and virXPathBoolean they forgot to do this on the error path. This
patch fixes this and move all ctxt->node = relnode instuctions just
after the xmlXPathEval() to make sure this doesn't happen if this code
is modified.