Fix memory leak that occurs when bc_tester_set_resource_dir_prefix() is called before bc_tester_parse_args(). Fix also the same leak with bc_tester_set_writable_dir_prefix().
Fix memory leak that occurs when bc_tester_set_resource_dir_prefix() is called before bc_tester_parse_args(). Fix also the same leak with bc_tester_set_writable_dir_prefix().