Yes, you can keep the unit testing out of your Cloud Manager, your build should successful with other checks (Security, Maintainability etc)
For Code Coverage you can get exception from AMS.
You can request AMS team to remove/override Code Coverage Metric from Cloud Manager.
Code Coverage is not mandatory to be onboarded an application to CM and this can be Overridden and keep it as a low priority.
Check with your AMS team for the process.