set timezone in EXTRA_JAVA_OPTS, too, when user uses menu 33 (#2141)

Signed-off-by: Markus Storm <markus.storm@gmx.net>

Author: mstormi

docs/openhabian.md

@@ -211,6 +211,9 @@ We try to setup everything for you so that you don't have to do any additional c
 -   **Language**: By default we set the `locale` setting to `en_US.UTF8` as this tends to be the best for error messages, it can be changed using menu option 32.
 -   **Passwords**: You should change the default password using menu option 34.
 
+NOTE: You should have been configuring timezone and locale at installation time via `openhabian.conf` settings.
+
+
 ##### Default Passwords
 
 For reference, the default username and passwords are as follows:
@@ -255,6 +258,9 @@ The ESPHome configuration files are secured by the openHABbian backup function.
 
 Many settings are configurable prior to the first boot of openHABian by changing the key value pairs in the `/boot/openhabian.conf` file on the SD card once you have flashed the initial image onto it.
 
+Most notably you should be setting the timezone and locale this way if yours differ from the defaults.
+Also make sure to read the [Networking] section and eventually preconfigure your Wi-Fi setup before you boot for the first time.
+
 Please note that - in case you use a Windows system for writing the SD card - the `/boot/` partition will be mounted to a drive named `bootfs`. So, e.g. if this drive has the letter `D:`, `/boot/openhabian.conf` will be found as `D:\openhabian.conf`.
 
 The openHABian configuration file uses key value pairs, essentially a list of `option=value` settings in a plain text file.

functions/system.bash

@@ -95,6 +95,12 @@ timezone_setting() {
   if [[ -n $INTERACTIVE ]]; then
     echo -n "$(timestamp) [openHABian] Setting timezone based on user choice... "
     if dpkg-reconfigure tzdata; then echo "OK ($(cat /etc/timezone))"; else echo "FAILED"; return 1; fi
+      echo -n "$(timestamp) [openHABian] Setting openHAB timezone... "
+
+      # tz sources order: 1) /etc/openhabian.conf  2) /etc/timezone  3) default UTC
+      tz=$(cat /etc/timezone 2>/dev/null); timezone=${timezone:=$tz}
+      if cond_redirect sed -ri "s|^(EXTRA_JAVA_OPTS.*?)(interning=true)?\"|\1\2 -Duser.timezone=${timezone:-UTC}\"|g" /etc/default/openhab; then echo "OK"; else echo "FAILED"; return 1; fi
+
   elif [[ -n $timezone ]]; then
     echo -n "$(timestamp) [openHABian] Setting timezone based on openhabian.conf... "
     if ! running_in_docker && ! running_on_github; then