Insufficient Access Rights to initiate a Directory Server restore after upgrade

Found with 7.0.0-SNAPSHOT rev. ba4c51292064b4fa62ffccaf15fd6080fb45d215.

With functional test which does upgrade from older version (tried 4.0.0 and 6.5.3) to 7.0.0 I can see a new error:

You have provided options for scheduling this operation as a task but options
provided for connecting to the server's tasks backend resulted in the
following error: 'Insufficient Access Rights: You do not have sufficient
privileges to initiate a Directory Server restore'

when trying to schedule an backup purge task with cmd:

./opendj/bin/dsbackup purge -h localhost -p 4444 -D "cn=myself" -w password -X  --backupLocation "/tmp/dsbackup_300" --backupId test1_20200724182431436

The same test just with --offline parameter works fine. 
I reported before this issue: https://bugster.forgerock.org/jira/browse/OPENDJ-7371

During a purge it requires restore privilege which doesn't look correct to me.

The issue was about missing upgrade task which was added and now we hit this issue. Without upgrade the test works just fine too.

Command to reproduce:
You will need to replace config.cfg by uploaded tmp.cfg

python3 run-pybot.py -v -s backends_group.dsBackupPurge -t purge_backup_id_online DJ

Steps:

1. Setup DJ (6.5.3)
2. Upgrade to 7.0.0
3. Create 2 new backends test1 and test2
4. Add data to test1 and test2
5. stop server
6. create offline backup of test1
7. start server
8. check with dsbackup list that backup exists
9. run the dsbackup purge cmd above