Add name of locked cron to cronlock

In cronlock there is the time the cron locked and a unique id.
My proposal is to change the unique id to the name of the cron who locked it.
The unique_id is not used anywhere and the name of the cron who locked is also unique.

In this way extension cronstatus can use it to show the correct cron who is locking.

Two little changes are necessary for this, see attachment