fix(dockerfile-linux): move configuration data into the image

Volumes should be used only for things that a containerized
application might change at runtime (e.g., `/var/lib/mysql`), not for
user configuration.  In particular, this `VOLUME` directive would
break a derivative image's ability to modify the configuation data.
Users can also mount any configuration data at runtime, making the
volume unnecessary.

Author: niheconomoum

Dockerfile-linux.template

@@ -121,7 +121,6 @@ RUN set -eux; \
 	cp -a /tmp/satosa/example /usr/share/satosa; \
 	rm -rf /tmp/satosa
 
-VOLUME /etc/satosa
 WORKDIR /etc/satosa
 
 COPY docker-entrypoint.sh /usr/local/bin/