Docker volume/mount point fixes per review.

https://github.com/docker-library/official-images/pull/4987#issuecomment-433185843

docker/1.5/Dockerfile

@@ -61,7 +61,7 @@ RUN set -x && \
       libwebsockets && \
 	rm -rf /build /etc/apk /lib/apk
 
-VOLUME ["/mosquitto/config", "/mosquitto/data", "/mosquitto/log"]
+VOLUME ["/mosquitto/data", "/mosquitto/log"]
 
 # Set up the entry point script and default command
 COPY docker-entrypoint.sh /

docker/1.5/README.md

@@ -2,9 +2,13 @@
 Containers built with this Dockerfile build as source from published tarballs.
 
 ## Mount Points
-Three docker volumes have been created in the image to be used for configuration, persistent storage and logs.
+A docker mount point has been created in the image to be used for configuration.
 ```
 /mosquitto/config
+```
+
+Two docker volumes have been created in the image to be used for persistent storage and logs.
+```
 /mosquitto/data
 /mosquitto/log
 ```