Comment 3 for bug 1709622

Hi CY,
that is odd - as if partially removed and the system is unsure in which state it is.
From your log:
Failed to stop mysql.service: Unit mysql.service not loaded.
invoke-rc.d: initscript mysql, action "stop" failed.
invoke-rc.d returned 5

Even on a non existing service that should work.

Could you run the following in a console and share the full output?:
$ systemctl status mysql
$ sudo invoke-rc.d mysql stop
$ systemctl stop mysql
$ systemctl status mysql