Improve instance-level services code
What does this MR do?
Fix specs saving an invalid service
After the changes in ab81251d the specs were misleading.
Multiple issue trackers for instance-level services
This is an improvement to the current code but not a change in the
behavior.
Right now we can have more than one issue tracker for instance-level
service because these services don't have a project. Here we are
skipping the callback (on: :manual_change
) to check for only one issue
tracker for those services and we are also being defensive with the
guard clause.
Remove unnecessary filtering of template false
After bf857f57, we also have a validation in place to be sure about it.
Related to: #208914 (closed) #199388 (closed)