Create test with adding nodegroup to operational environment

We need to create (or modify one of 2 existing) auto test for adding new nodegroups to deployed environment.

Scenario:

Create environment
Add nodes from 'default' nodegroup
Run network verification
Deploy environment
Run network verification
Run OSTF
Create new 'custom' nodegroup for the environment and configure its networks
Add nodes from 'custom' nodegroup to the environment
Run network verification
Deploy changes
Run network verification
Run OSTF
Check that nodes from 'default' nodegroup can reach nodes from 'custom' nodegroup via management and storage networks (check route presence, verify by ping)