There is a bug that makes `custom-first-boot` service stay in services when the first boot script is removed.

How to reproduce:
1. create a blueprint with a first boot script
2. download the blueprint and confirm `custom-first-boot` was added to enabled services
3. click on "Edit blueprint"
4. go to First boot step and remove the script
5. save edited blueprint

Current behaviour:

• `custom-first-boot` service should be still enabled even with the removed first boot script

Updated behaviour:

• `custom-first-boot` is no longer in the blueprint after first boot script got removed