opensearch: set OPENSEARCH_INITIAL_ADMIN_PASSWORD

Since 2.12 OpenSearch requires setting initial admin password,
that is not trivial/weak.

Closes-Bug: #2054586

Change-Id: I6b6ef656bc2009a2dc3cdfcb01956d50fba4b7b9
(cherry picked from commit 756ee984c3)

docker/opensearch/opensearch/Dockerfile.j2

@@ -14,6 +14,8 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
         'opensearch'
     ] %}
 
+ENV OPENSEARCH_INITIAL_ADMIN_PASSWORD="Kolla24OpenSearch"
+
 {{ macros.install_packages(opensearch_packages | customizable("packages")) }}
 
 COPY extend_start.sh /usr/local/bin/kolla_extend_start