[sfc] Remove unused router related methods

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

Removed methods:
   * _update_router_admin_state

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

[1] https://docs.openstack.org/releasenotes/tempest

Change-Id: I8446937a3e9aeea1375b725e8bd812f663f36beb
1 file changed