Revert "Bump Atomix dependency version to 3.1.6"

This reverts commit 3dbb14964a1a1742923c4c98622338701cfd1e8f.

Change-Id: I6d1bba0470b6b371d1fffdb832f3441f5864f92d
diff --git a/tools/test/bin/atomix-push-bits b/tools/test/bin/atomix-push-bits
index 014bc0b..e0375bd 100755
--- a/tools/test/bin/atomix-push-bits
+++ b/tools/test/bin/atomix-push-bits
@@ -26,7 +26,7 @@
 
 . $ONOS_ROOT/tools/build/envDefaults
 
-ATOMIX_VERSION=${ATOMIX_VERSION:-3.1.6}
+ATOMIX_VERSION=${ATOMIX_VERSION:-3.1.5}
 ATOMIX_MAVEN=~/.m2/repository/io/atomix/atomix-dist/$ATOMIX_VERSION/atomix-dist-$ATOMIX_VERSION.tar.gz
 ATOMIX_LOCAL=/tmp/atomix-$ATOMIX_VERSION.tar.gz
 ATOMIX_REMOTE=https://oss.sonatype.org/content/repositories/releases/io/atomix/atomix-dist/$ATOMIX_VERSION/atomix-dist-$ATOMIX_VERSION.tar.gz