Update the TESTING.rst file to reflect that just installing and
starting zookeeperd is no longer sufficient now that we require TLS
and auth for the connection. Suggest the container-based setup
script instead. Also improve that script to allow it to be invoked
as a normal user, with root command escalation tool choice (e.g.
"sudo") supplied through a ROOTCMD environment variable, so that
things created inside the git worktree like the CA don't end up
root-owned.
Change-Id: Ia00f5514ba0bd97b2ef17fb798b7c2dc68d9a55e
d23662e50f