Move scylla-server and scylla-jmx supervisord config files to separate
files and make the main supervisord.conf scan /etc/supervisord.conf.d/
directory. This makes it easier for people to extend the Docker image
and add their own services.
Message-Id: <1471588406-25444-1-git-send-email-penberg@scylladb.com>
(cherry picked from commit 9d1d8baf37)