logstash: pin to 7.9.* for Elasticsearch OSS compatibility

The latest versions of logstash 7.x do not support using the OSS version
of Elasticsearch, and fail to push logs if an OSS version is used. This
prevents Monasca log API from working correctly.

This change fixes the issue by pinning logstash-oss to 7.9.x, the most
recent available package in the repo that still supports Elasticsearch
OSS.

NOTE: logstash 7.11 introduced the breaking change, however 7.10 is
unavailable in the package repos.

Change-Id: I4ec4eb837c98f57964488769ab82ba8213ad582c
Closes-Bug: #1941754

docker/base/apt_preferences.debian

@@ -11,3 +11,9 @@ Pin-Priority: 1000
 Package: td-agent*
 Pin: version 4.0.*
 Pin-Priority: 1000
+
+# NOTE(mgoddard): logstash 7.9.x is the last version that supports
+# Elasticsearch OSS.
+Package: logstash-oss
+Pin: version 7.9.*
+Pin-Priority: 1000

docker/base/apt_preferences.ubuntu

@@ -10,3 +10,9 @@ Pin-Priority: 1000
 Package: td-agent*
 Pin: version 4.0.*
 Pin-Priority: 1000
+
+# NOTE(mgoddard): logstash 7.9.x is the last version that supports
+# Elasticsearch OSS.
+Package: logstash-oss
+Pin: version 7.9.*
+Pin-Priority: 1000

docker/logstash/Dockerfile.j2

@@ -19,9 +19,17 @@ ENV JAVA_HOME /usr/lib/jvm/jre-11-openjdk/
 ENV JAVA_HOME /usr/lib/jvm/java-11-openjdk-{{debian_arch}}/
 {% endif %}
 
+# NOTE(mgoddard): logstash 7.9.x is the last version that supports
+# Elasticsearch OSS.
+{% if base_package_type == 'rpm' %}
+{% set logstash_packages = [
+    'logstash-oss-7.9.*',
+] %}
+{% else %}
 {% set logstash_packages = [
     'logstash-oss',
 ] %}
+{% endif %}
 
 # Post-install script of Logstash fails when trying to install Logstash and
 # Java together.

releasenotes/notes/logstash-7.9-30fd90e921037a8a.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes an issue with the logstash image which was incompatible with the last
+    OSS version (7.10) of Elasticsearch. Logstash is now pinned to 7.9.
+    `LP#1941754 <https://bugs.launchpad.net/kolla/+bug/1941754>`__