Please do not crosspost the identical question all over the internet!
This question was answered on slack with this:
As far as I remember, clustering came back in later during the 7.0
phase. And as there is a very
important security fix for 7.0 GA7, you should upgrade anyway.
After that, please don't rely on old server-side software continued to
be fixed and prepare to stay on a more recent version - Your version
is from June 2016, the latest (patched) 7.0 GA7 is dated May 2018, and
the patch is 8 months old - that should have been enough time to patch
