Fix problem with specifying vardir, mysql_version_id was not yet available when vardir arguments is checked
Move the code to look for exe_mysqld earlier => to initial_setup
Fix warnings detected by running with "diagnostics"
Remove unused option "opt_result_ext"
Init "path_ndb_examples_dir"


mysql-test/lib/mtr_cases.pl:
  Set default number of slave to 0
  Remove unused/uninitialized "$opt_result_ext"
mysql-test/lib/mtr_report.pl:
  Remove unused/uninitialized "$opt_result_ext"