Add releasenote to tag the Tempest for Stein release

This commit adds the releasenote to tag Tempest for Stein
and needed for version 20.0.0 to release.

This relesenote also mark end of support for Ocata release as
ocata is in EM state.

Once we release the Tempest 20.0.0, we will remove the ocata job
from master gate.

Change-Id: I93bf37e31497881536b85783dc3cff70a56b04cb
1 file changed