[sfc] Remove _get_network_by_name & check_floating_ip_status

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

Removed methods:
    * _get_network_by_name
    * check_floating_ip_status

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: Ib01030cf424f96fbcaaa173f0f755e80057c2cdf
1 file changed