[sfc] Remove unused check_remote_connectivity methods

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

Removed methods:
    * _check_remote_connectivity
    * check_remote_connectivity

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: I6e0a805520948086379f0e5537e12dedcd093e50
1 file changed