Install RabbitMQ repo key on Ubuntu and Debian

It was missed previously.
CI did not detect it because it ignores apt security issues.
That gets fixed in Ic5abc4b87fd76f87aba383abf43e95ba70629fcb

Change-Id: I11256c674c42e35496146ff64fee1e8e04c30d2c
(cherry picked from commit 4443139)

Author: yoctozepto

docker/base/Dockerfile.j2

@@ -341,7 +341,8 @@ COPY apt_preferences /etc/apt/preferences.d/kolla-custom
     {# 901F9177AB97ACBE                         -- Treasure Data, Inc (Treasure Agent Official Signing key) <[email protected]> #}
     {# A20F259AEB9C94BB                         -- Sensuapp (Freight) <[email protected]> #}
     {# F1656F24C74CD1D8                         -- MariaDB Signing Key <[email protected]> #}
-    {# F77F1EDA57EBB1CC                         -- RabbitMQ Signing Key <[email protected]> #}
+    {# F77F1EDA57EBB1CC                         -- Launchpad RabbitMQ Erlang PPA key #}
+    {# F6609E60DC62814E                         -- PackageCloud RabbitMQ repository key #}
     {% set base_apt_keys = [
       '391A9AA2147192839E9DB0315EDB1B62EC4926EA',
       '46095ACC8548582C1A2699A9D27D666CD88E42B4',
@@ -352,6 +353,7 @@ COPY apt_preferences /etc/apt/preferences.d/kolla-custom
       'A20F259AEB9C94BB',
       'F1656F24C74CD1D8',
       'F77F1EDA57EBB1CC',
+      'F6609E60DC62814E',
     ] %}
     {% set remote_apt_keys = [
       'https://packages.grafana.com/gpg.key',
@@ -361,6 +363,7 @@ COPY apt_preferences /etc/apt/preferences.d/kolla-custom
     {% set base_apt_keys = [
       '46095ACC8548582C1A2699A9D27D666CD88E42B4',
       'F77F1EDA57EBB1CC',
+      'F6609E60DC62814E',
     ] %}
     {% set remote_apt_keys = [
       'https://download.docker.com/linux/debian/gpg',