Remove get_remote_client method

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

Replaced methods:
	* get_remote_client

Related tempest commit:
https://opendev.org/openstack/tempest/commit/f52c759e5cc6da962ad63831c55dc140d05a2373

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: Iab28d75999ae408a8bbefab76319f384e49cbcc0
3 files changed