Remove _create_network & _get_server_port_id_and_ip4 methods

As tempest.scenario.manager was announced stable interface in Tempest 27.0.0[1] it can be now reused in plugins.

Replaced methods:
	* _create_network
	* _get_server_port_id_and_ip4

Etherpad concerning this effort:
https://etherpad.opendev.org/p/tempest-scenario-manager-cleanup

[1] https://docs.openstack.org/releasenotes/tempest/v27.0.0.html#release-notes-27-0-0

Change-Id: I424cf6f3547eeb229f888e4ad9f9cb09f635ec31
3 files changed