prelude: |
    Welcome to the Ussuri release of the OpenStack Block Storage service
    (cinder).  The cinder team would like to bring the following points
    to your attention.  Details may be found below.

    * With this release, the Block Storage API version 3 has reached
      microversion **3.60**.

    * Python 2 is no longer supported.  The minimum version of Python
      that may be used with this release is **Python 3.6**.

    * The unsupported driver removal policy has been revised.  See the
      "Known Issues" section of this document for more information.

Add ussuri prelude to release notes
Add ussuri prelude to release notes

Change-Id: I83a38e4d888fa94bb81527b07c6db0a59c11a78c
