Move fetching response from channel to request() method

Also parse error on bad status in request method.
This pattern was scattered all over the place.

internal/lvgen/procedures.tmpl

@@ -140,17 +140,11 @@ func (l *Libvirt) {{.Name}}({{range $ix, $arg := .Args}}{{if $ix}}, {{end}}{{.Na
 		return
 	}
 {{end}}
-	var resp <-chan response
-	resp, err = l.request({{.Num}}, constants.Program, &buf)
+{{if .RetStruct}}	var r response{{end}}
+	{{if .RetStruct}}r{{else}}_{{end}}, err = l.request({{.Num}}, constants.Program, &buf)
 	if err != nil {
 		return
 	}
-
-	r := <-resp
-	if r.Status != StatusOK {
-		err = decodeError(r.Payload)
-		return
-	}
 {{if .RetStruct}}
 	// Return value unmarshaling
 	rdr := bytes.NewReader(r.Payload)