[sfc] Remove create_networks & create_floating_ip

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

Removed methods:
    * create_networks
        - Renamed to setup_network_subnet_with_router in Tempest
    * create_floating_ip

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: I7e0128e7ee080c44f4d6ccec74083c17864c3d7b
2 files changed