Fixed innodb.help_url failure.

mysql-test/suite/innodb/r/help_url.result:
  Accessing discarded tablespace doesn't cause loud error message anymore.
  Use different way to retrieve refman link.
mysql-test/suite/innodb/t/help_url.test:
  Accessing discarded tablespace doesn't cause loud error message anymore.
  Use different way to retrieve refman link.