- fixed accidently deleting mysql r/o user completely when it is removed from a single database, fixes #4963

Fixed a problem that caused the creation of mysql users to fail. This affected the dev branch only and not the stable 3.1.6 release.

How to reproduce issue

- Fixed mysql privilege reduction

FS#3830 - Password is not updated in `mysql`.`user` table when read-only database user's password is changed

Fixed: db user not created in mysql user table if password is stored in cleartext (ISPConfig < 3.0.3.3)
Fixed: db user not created on update if status not changed (e. g. on using resync tool)

Bugfix on db-Class (datalog Update)

- Added "actions" framework in server to replace the functions provided by the core modules
- Moved system update function from remoteactins core module to software update plugin.

and make changes to mysql users in the mysql plugin module.

Refs: 1722

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