Move `org-toggle-sticky-agenda' again and autoload it

The previous related commit was to prevent an error
when M-x org-reload RET was reloading org files from
an ELPA directory.  We now autoload the function so
that it is know by the time org-reload might be called.

lisp/org-agenda.el

@@ -1852,6 +1852,8 @@ works you probably want to add it to `org-agenda-custom-commands' for good."
 
 
 ;;; Multiple agenda buffers support
+
+;;;###autoload
 (defun org-toggle-sticky-agenda (&optional arg)
   "Toggle `org-agenda-sticky'."
   (interactive "P")