Run SetConfig on a separate task

[imobachgs]

Problems

• It is not possible to load a profile when it does not contain product definition (bsc#1257067, bsc#1257082).
• Bootloader SetConfig should be executed after storage SetConfig.
• Using "agama questions" in a pre-script causes Agama to hang.

Solution

• Allow not setting a product in the profile.
• Move the SetConfig stuff to a separate task.
• Run pre-scripts only once to prevent potential infinite loops. Otherwise, we can get into an infinite loop when using "agama config load" (unexpected) or "agama questions" in a pre-script.

Testing

• Added a new unit test
• Tested manually

Follow-up

• Reset the proposal and software configuration when issuing a PUT with no product.
• The changes by agama questions mode non-interactive will get applied after loading the configuration.

[jreidinger]

note Bootloader SetConfig should be executed after software SetConfig. is not correct as it is storage and not software.

[imobachgs]

note Bootloader SetConfig should be executed after software SetConfig. is not correct as it is storage and not software.

Yes, right, I have updated the description.