[sfc] Remove create_server & get_remote_client

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

Removed methods:
    * create_server
    * get_remote_client

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: If2566d6262cf2b40487acbfe2eb2329d0977e0dd
1 file changed