Bump Atomix dependency version to 3.1.6

Change-Id: I993e893dd483b695d38018e97c981ca0525d0354
diff --git a/tools/test/bin/atomix-push-bits b/tools/test/bin/atomix-push-bits
index e0375bd..014bc0b 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=${ATOMIX_VERSION:-3.1.5}
+ATOMIX_VERSION=${ATOMIX_VERSION:-3.1.6}
 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