MDEV-15675 encryption.innodb_encryption failed in buildbot with timeout

Test case fail to include undo tablespace while waiting for the
encryption thread to encrypt all existing tablespace

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

@@ -19,7 +19,7 @@ innodb_system
 # Success!
 # Now turn off encryption and wait for threads to decrypt everything
 SET GLOBAL innodb_encrypt_tables = off;
-# Wait max 10 min for key encryption threads to encrypt all spaces
+# Wait max 10 min for key encryption threads to decrypt all spaces
 SELECT NAME FROM INFORMATION_SCHEMA.INNODB_TABLESPACES_ENCRYPTION WHERE MIN_KEY_VERSION = 0
 AND NAME NOT LIKE 'innodb_undo%' AND NAME NOT LIKE 'mysql/innodb_%_stats';
 NAME

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

@@ -14,7 +14,9 @@ SHOW VARIABLES LIKE 'innodb_encrypt%';
 
 SET GLOBAL innodb_encrypt_tables = ON;
 
---let $tables_count= `select count(*) + 1 from information_schema.tables where engine = 'InnoDB'`
+let $undo_count= `select @@global.innodb_undo_tablespaces`;
+
+--let $tables_count= `select count(*) + 1 + $undo_count from information_schema.tables where engine = 'InnoDB'`
 
 --echo # Wait max 10 min for key encryption threads to encrypt all spaces
 --let $wait_timeout= 600
@@ -33,7 +35,7 @@ AND NAME NOT LIKE 'innodb_undo%' AND NAME NOT LIKE 'mysql/innodb_%_stats';
 --echo # Now turn off encryption and wait for threads to decrypt everything
 SET GLOBAL innodb_encrypt_tables = off;
 
---echo # Wait max 10 min for key encryption threads to encrypt all spaces
+--echo # Wait max 10 min for key encryption threads to decrypt all spaces
 --let $wait_timeout= 600
 --let $wait_condition=SELECT COUNT(*) = 0 FROM INFORMATION_SCHEMA.INNODB_TABLESPACES_ENCRYPTION WHERE MIN_KEY_VERSION <> 0;
 --source include/wait_condition.inc