No need to mask the error code returned by getting the next row to end of file when
doing filesort.

mysql-test/r/innodb_mysql_rbk.result:
  Bug #41543: test case
mysql-test/t/innodb_mysql_rbk-master.opt:
  Bug #41543: test case
mysql-test/t/innodb_mysql_rbk.test:
  Bug #41543: test case
sql/filesort.cc:
  Bug #41543: No need to mask the error code returned by getting the next row to end of file when
  doing filesort.