abitest: more assertive leak checks
abitest: more assertive leak checks

Mark various tests that create pseudo-Nodes as being expected to have no
net change on the numbers of Nodes and channels in the Runtime.

This ensures that various failure cases clean up after themselves properly.

project-oak/oak,project-oak/oak,project-oak/oak,project-oak/oak,project-oak/oak,project-oak/oak,project-oak/oak