tests: wait_for_service shows status after actual first minute
The wait_for_service function shows the status of a service once a
minute, as it waits for the service status to change. Due to a simple
mistake the status was printed at iteration zero as well, spamming logs
with useless information in a normal situation.
Signed-off-by: Zygmunt Krynicki <email address hidden>
This introduces the concept of a SnapRef(erence) with a new interface. The main goal here is to be able to write code that can work both in cases where a snap id is known for some snaps or the name only.
This will now be the case for code that deals with model assertions, so far they carried only names but for Core 20 they will carry snap ids for the grade stable at least.
This is introduces also SnapSet to be able to work with a set of these.
image: support prepare-image --classic for snapd snap only images
To do this, the changes start with a refactor of how we emit seed.yaml to be based on stable sorting by type, this is the same sorting used at first boot time.
Consequently:
* we need to respect the user ordering but don't need to agonize on details
* we are able to move to later the decision whether on classic we need
to add implicitly snapd or core, this is unavoidable because it requires to
have seen all other snaps and their requirements
* later this should also allow to correctly fetch prerequisites for
extra snaps vs required/from the model snaps
