Fill schema tables with data before filesort if it's necessary


mysql-test/r/information_schema.result:
  Fix for bug#15307 GROUP_CONCAT() with ORDER BY returns empty set on information_schema(2nd ver)
    test result
mysql-test/t/information_schema.test:
  Fix for bug#15307 GROUP_CONCAT() with ORDER BY returns empty set on information_schema(2nd ver)
    test case