[SDFAB-933] Integrate atomix-3.1.12 and expose demote API

Additionally, this patch adds unit tests for demote and
updates a bunch of testing tools

Change-Id: I6c4046730707fa3ac88bbd2bcaf2f60250baa899
diff --git a/tools/dev/docker/Dockerfile-sshd b/tools/dev/docker/Dockerfile-sshd
index 2229787..6f0c00c 100644
--- a/tools/dev/docker/Dockerfile-sshd
+++ b/tools/dev/docker/Dockerfile-sshd
@@ -2,9 +2,9 @@
 LABEL maintainer="Eric Tang <qcorba at gmail.com>"
 
 ARG ATOMIX_VERSION
-ENV ENV_ATOMIX_VERSION=${ATOMIX_VERSION:-3.1.9}
+ENV ENV_ATOMIX_VERSION=${ATOMIX_VERSION:-3.1.12}
 
-RUN apt-get update 
+RUN apt-get update
 RUN DEBIAN_FRONTEND=noninteractive apt-get -y install \
     --no-install-recommends \
     openjdk-11-jre \
@@ -66,7 +66,7 @@
 
 # Install Atomix
 RUN set -eux; \
-#   curl -o /tmp/atomix.tar.gz -XGET https://oss.sonatype.org/content/repositories/releases/io/atomix/atomix-dist/3.1.9/atomix-dist-3.1.9.tar.gz; \
+#   curl -o /tmp/atomix.tar.gz -XGET https://oss.sonatype.org/content/repositories/releases/io/atomix/atomix-dist/3.1.12/atomix-dist-3.1.12.tar.gz; \
     curl -o /tmp/atomix.tar.gz https://repo1.maven.org/maven2/io/atomix/atomix-dist/$ENV_ATOMIX_VERSION/atomix-dist-$ENV_ATOMIX_VERSION.tar.gz; \
     mkdir /opt/atomix; \
     tar zxmf /tmp/atomix.tar.gz -C /opt/atomix; \