Remove check_remote_connectivity related  methods

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

Replaced methods:
	* _check_remote_connectivity
	* check_remote_connectivity (not used)

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: Idd323660b21ea109d5f24efc0edab216723c8dca
1 file changed