syncthing: configuration cleanup & hardening

Run the service under an unprivileged
user account

The following parameters are now configurable
  niceness
  max concurrency (defaults to number of CPUs)
  user

Added flags "-no-browser"
Disabled in-place upgrades (disabled in the
build already)

Redirected stderr/stdout to syslog

Added support for "reload_config"

Increased "term_timeout" to 15s to give it
plenty of time to shut down gracefully

Properly handled non-existing directories

Removed a softlink that assumes a specific naming
convention in syncthing

Added a comment that using external storage is a
recommend configration

Signed-off-by: Marc Benoit <marcb62185@gmail.com>
[increased package release]
Signed-off-by: Paul Spooren <mail@aparcar.org>
(cherry picked from commit a9443eb0eb)
Tested-by: Marc Benoit <marcb62185@gmail.com>

utils/syncthing/files/etc/config/syncthing

@@ -3,5 +3,24 @@ config syncthing 'syncthing'
 	option enabled '0'
 
 	option gui_address 'http://127.0.0.1:8384'
-	option home '/etc/syncthing/'
+
+	# Use internal flash for evaluation purpouses. Use external storage
+	#   for production.
+	# This filesystem must either support ownership/attributes or
+	#   be readable/writable by the user specified in
+	#   'option user'.
+	# Consult syslog if things go wrong.
+	option home '/etc/syncthing'
+
+	# Changes to "niceness"/macprocs are not picked up by "reload_config"
+	#   nor by "restart": the service has to be stopped/started
+	#   for those to take effect
+	option nice '19'
+
+	# 0 to match the number of CPUs (default)
+	# >0 to explicitly specify concurrency
+	option macprocs '0'
+
+	# Running as 'root' is possible, but not recommended
+	option user 'syncthing'