Add ARCHIVE_SERVER to rclone section

The archive-is-reachable.sh script for rclone pings $ARCHIVE_SERVER
to check if the server is reachable, so add that to the rclone
section in the config.

pi-gen-sources/00-teslausb-tweaks/files/teslausb_setup_variables.conf.sample

@@ -32,6 +32,7 @@ export SHARE_PASSWORD='password'
 
 # Variables for rclone archiving
 #export ARCHIVE_SYSTEM=rclone
+#export ARCHIVE_SERVER=rclone_server_name_or_ip
 #export RCLONE_DRIVE="remotename"
 #export RCLONE_PATH="remotepathname"
 # The following is optional