BUG #5831 Changed mysql_revoke_all() to successfully delete all privileges for a user in one pass.


sql/sql_acl.cc:
  BUG #5831 Changed mysql_revoke_all() to successfully delete all privileges for a user in one pass.
mysql-test/r/grant.result:
  BUG #5831 Changed mysql_revoke_all() to successfully delete all privileges for a user in one pass.
mysql-test/t/grant.test:
  BUG #5831 Changed mysql_revoke_all() to successfully delete all privileges for a user in one pass.