- Moved code to set 'need_relay_log_purge' variable
  from change_execute_options() to have_execute_option().
- Removed 'ret' variable from change_master().
- Removed mysql_cond_broadcast(&mi->data_cond);
  This has no listener.
- Modified the signature of set_password().
  The second argument was not being used so removed it.
  The callers always make sure NULL is not being passed
  as password, so added an assert for the same. 
- Improved tests comments.
- Fixed indentation issues.