Correct html export of todo keywords

* org-html.el (org-export-as-html): Apply
  `org-export-html-get-todo-kwd-class-name' to the class
  attribute of the todo-keyword span tag, not to its text content.

The problem was that special characters in todo keywords were being
replaced by underscore. This was meant to happen to the class
attributes set around them.

TINYCHANGE

This only swaps two arguments to a concat.

lisp/org-html.el

@@ -1628,9 +1628,9 @@ PUB-DIR is set, use this as the publishing directory."
 			    (if (member (match-string 2 line)
 					org-done-keywords)
 				"done" "todo")
-			    " " (match-string 2 line)
-			    "\"> " (org-export-html-get-todo-kwd-class-name
-				    (match-string 2 line))
+			    " " (org-export-html-get-todo-kwd-class-name
+				 (match-string 2 line))
+			    "\"> " (match-string 2 line)
 			    "</span>" (substring line (match-end 2)))))
 
 	  ;; Does this contain a reference to a footnote?