magnum: fix issue with keystone auth default policy

Closes-Bug: #1957159
Change-Id: I042da2234d0a06f1b7ddcac9eb6db8b86f13d205
(cherry picked from commit 0a536f4)

Author: mnasiadka

docker/magnum/magnum-base/Dockerfile.j2

@@ -32,6 +32,7 @@ RUN ln -s magnum-base-source/* magnum \
     && {{ macros.install_pip(magnum_base_pip_packages | customizable("pip_packages")) }} \
     && mkdir -p /etc/magnum \
     && cp -r /magnum/etc/magnum/* /etc/magnum \
+    && mv /etc/magnum/keystone_auth_default_policy.sample /etc/magnum/keystone_auth_default_policy.json \
     && chown -R magnum: /etc/magnum
 
 {% endif %}

releasenotes/notes/magnum-keystone-auth-default-policy-e16f7bb558aa4b14.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixes an issue with missing Magnum Keystone auth default policy.
+    `LP#1957159 <https://launchpad.net/bugs/1957159>`__