Document howto create a release patch.

howto/code/release-bugfix.rst
release_notes/voltha_2.12.rst
-----------------------------
  o Detail branch creation attached to branch=voltha-2.12.
  o Add suggested for howto sanity check git attributes
    and sandbox files.

Change-Id: I4d0f63037e0ca2f324e561ad26e66b9a9dfec4df
diff --git a/release_notes/voltha_2.12.rst b/release_notes/voltha_2.12.rst
index a0067c8..6d5708e 100644
--- a/release_notes/voltha_2.12.rst
+++ b/release_notes/voltha_2.12.rst
@@ -332,7 +332,7 @@
      -
      -
      - ``N``
-   * - `Bbsim-sadis-server <https://gerrit.opencord.org/gitweb?p=bbsim-sadis-server.git;a=tree>`_
+   * - `Bbsim-sadis-server <https://gerrit.opencord.org/gitweb?p=bbsim-sadis-server.git;a=tree>`__
      -
      - ``0.3.4``
      - `0.3.2 <https://gerrit.opencord.org/plugins/gitiles/voltha-helm-charts/+/refs/heads/master/bbsim-sadis-server/Chart.yaml>`_