Splits network_basic_ops to fully isolated test cases

Splits network basic ops to smaller test cases sharing code while tests
pass.
Due to network_basic_ops getting too complicated for its name

Test cases are fully isolated. No resource sharing.

Partially Implements: blueprint neutron-advanced-scenarios

Change-Id: I1939f743b0335181e95924c2c5cb0bb259ae720e
Merge "Splits network_basic_ops to fully isolated test cases"