Remove check_public_network_connectivity & _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:
	* check_public_network_connectivity
		- not used
	* _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: I473390048308a9637ead542ed18495cffb320dbc
1 file changed