tests: convert extra-vars to use json

tests: convert extra-vars to use json

This will prevent ansible from misreading any of these values. There
were failures with xenial deployments because the value set for
``ceph_rhcs`` was being treated as a boolean True even though I'd set
the value to false. This is because boolean values passed in with
--extra-vars must use the json format.

The formatting of the json is very important as you need a '\' to escape
the starting and ending json to make tox happy. Also, each line needs to
end with '\' if it's a multi-line command.

Another thing to note is that if you want to use extra vars at the
command line to respond to a vars_prompt it must be in key/value format.
This is why we have a -e and a --extra-vars on the purge and update
tests.

Signed-off-by: Andrew Schoen <aschoen@redhat.com>