mosquitto: disable connection_message logging

* Connection messages may cause unnecessary flash wear
* Fix docs to be precise about how docker log persistence

Author: ukkopahis

.templates/mosquitto/iotstack_defaults/config/mosquitto.conf

@@ -14,6 +14,9 @@ persistence_location /mosquitto/data
 log_dest stdout
 log_timestamp_format %Y-%m-%dT%H:%M:%S
 
+# Reduce size and SD-card flash wear, safe to remove if using a SSD
+connection_messages false
+
 # password handling:
 #   password_file commented-out allow_anonymous true =
 #     open access

docs/Containers/Mosquitto.md

@@ -209,10 +209,12 @@ Using `mosquitto.conf` as the example, assume you wish to use your existing file
 
 Mosquitto logging is controlled by `mosquitto.conf`. This is the default configuration:
 
-```
+```apacheconf
 #log_dest file /mosquitto/log/mosquitto.log
 log_dest stdout
 log_timestamp_format %Y-%m-%dT%H:%M:%S
+# Reduce size and SD-card flash wear, safe to remove if using a SSD
+connection_messages false
 ```
 
 When `log_dest` is set to 	`stdout`, you inspect Mosquitto's logs like this:
@@ -221,7 +223,9 @@ When `log_dest` is set to 	`stdout`, you inspect Mosquitto's logs like this:
 $ docker logs mosquitto
 ```
 
-Logs written to `stdout` are ephemeral and will disappear when your Mosquitto container is rebuilt, but this type of configuration reduces wear and tear on your SD card.
+Logs written to `stdout` are stored and persisted to disk as managed by Docker.
+They are kept over reboots, but are lost when your Mosquitto container is
+removed or updated.
 
 The alternative, which *may* be more appropriate if you are running on an SSD or HD, is to change `mosquitto.conf` to be like this:
 
@@ -246,7 +250,7 @@ $ sudo tail ~/IOTstack/volumes/mosquitto/log/mosquitto.log
 
 > You need to use `sudo` because the log is owned by userID 1883 and Mosquitto creates it without "world" read permission.
 
-Logs written to `mosquitto.log` do not disappear when your IOTstack is restarted. They persist until you take action to prune the file.
+Logs written to `mosquitto.log` persist until you take action to prune the file.
 
 ## Security
 
@@ -699,7 +703,7 @@ If you have a use-case that needs port 9001, you can re-enable support by:
 
 2. Inserting the additional listener in `mosquitto.conf`:
 
-	```
+	```apacheconf
 	listener 1883
 	listener 9001
 	```