Prepare binlogrouter for removal of router_options

To prepare the router's for the eventual removal of the router_options
parameter, the API option arguments should not be used. The parameters can
be substituted by tokenizing the value of the parameter that is still
stored as a part of the service.

server/modules/routing/binlogrouter/blr_file.cc

@@ -3799,7 +3799,7 @@ const char *blr_get_encryption_algorithm(int algo)
  * @param name   The algorithm string
  * @return       The numeric value or -1 on error
  */
-int blr_check_encryption_algorithm(char *name)
+int blr_check_encryption_algorithm(const char *name)
 {
     if (name)
     {