fix encryption.tempfiles to check that encrypt_tmp_files is ON

mysql-test/suite/encryption/r/tempfiles.result

+select @@encrypt_tmp_files;
+@@encrypt_tmp_files
+1
 CREATE TABLE t1(a INT);
 INSERT INTO t1 VALUES(1),(2);
 DELETE FROM t1 WHERE a=1;

mysql-test/suite/encryption/t/tempfiles.opt

+--encrypt-tmp-files

mysql-test/suite/encryption/t/tempfiles.test

@@ -11,6 +11,8 @@ source include/have_binlog_format_row.inc;
 # engine. But there's no need to run it twice for InnoDB and XtraDB.
 source include/have_xtradb.inc;
 
+select @@encrypt_tmp_files;
+
 #
 # MyISAM messing around with IO_CACHE::file
 #