Make self-update rollback option a flag
Make self-update rollback option a flag

The command's rollback option accepted a value, which wasn't not very clear to the user. Only when the user specified a truthy value is the rollback performed. This commit changes it to a flag. Its resulting boolean value is used to decide whether to upgrade or to roll back.

ibuildingsnl/qa-tools,ibuildingsnl/qa-tools,ibuildingsnl/qa-tools