Add an instance type that is excluded from network restrictions

[mojtaba-esk]

Since we removed the Executor instance type, there is a need to have a type to be excluded from network restrictions.

This gave us the possibility to disable networking between Instances without disabling networking from and to executor instances. We would lose this ability.

The question is if we need the scenario where we disable the networking of a node for a certain time to simulate network connection loss.

Originally posted by @smuu in #508 (comment)