Allow for redirects to ftp servers

The Fedora image can redirect to a ftp server, in which case outputs a
213 if not modified.

Change-Id: I714fc3562bf188994357e1918af309d8edeecde5

elements/cache-url/bin/cache-url

@@ -46,7 +46,9 @@ if [ "$rcode" = "200" ] ; then
         echo $success
         mv $tmp $dest
     fi
-elif [ "$rcode" = "304" ] ; then
+# 213 is the response to a ftp MDTM command, curl outputs a 213 as the status
+# if the url redirected to a ftp server and Not-Modified
+elif [ "$rcode" = "304" -o "$rcode" = "213" ] ; then
     echo "Server copy has not changed. Using locally cached $url"
     rm -f $tmp
 else