[sfc] Remove _get_server_port_id_and_ip4 & check_vm_connectivity

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

Removed methods:
    * _get_server_port_id_and_ip4
    * check_vm_connectivity

There is a slight difference between tempest's
_get_server_port_id_and_ip4 and this one.
Most changes are just fixes, without bigger logical interference.
See some of the related patches below.[2][3]

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
[2] https://opendev.org/openstack/tempest/commit/5c191faae78f52f876edba72484ea644d3df04fd
[3] https://opendev.org/openstack/tempest/commit/95a3169e1782f31c794e56cb836c1d9476a0adf8

Change-Id: I6a7268784b8a915aab665db1bc00e764f40986ef
2 files changed