software/selenium_client: add pos files for tail plugin

Use position files for Fluentd tail plugin to avoid sending data twice
when Fluentd service is restarted.

software/selenium_client/buildout.hash.cfg

@@ -14,4 +14,4 @@
 # not need these here).
 [instance-selenium]
 filename = instance.cfg
-md5sum = e9414172af42c1e8a483286716ed7370
+md5sum = 80c32e1a77cfab9e6df77fd4c145deeb

software/selenium_client/instance.cfg

@@ -17,6 +17,7 @@ context =
   key slapparameter_dict slap-configuration:configuration
   key simulation_log_dir directory:simulation-log-dir
   key flight_log_dir directory:flight-log-dir
+  key tmp_dir directory:tmp
 inline =
   {% set wendelin_url = slapparameter_dict.get('wendelin-url', '') -%}
   {% set wendelin_user = slapparameter_dict.get('wendelin-user', '') -%}
@@ -27,6 +28,7 @@ inline =
     @type tail
     read_from_head true
     path {{ simulation_log_dir }}/*.log
+    pos_file {{ tmp_dir }}/drone_simulation.pos
     tag drone_simulation.sample-drone-raw-data
     format none
     path_key filepath
@@ -48,6 +50,7 @@ inline =
     @type tail
     read_from_head true
     path {{ flight_log_dir }}/*.log
+    pos_file {{ tmp_dir }}/drone_real.pos
     tag drone_real.bouncy_flight_mavsdk_raw_data
     format none
     path_key filepath
@@ -66,6 +69,7 @@ inline =
   </match>
 
 [directory]
+tmp = $${:home}/tmp
 simulation-log-dir = $${:etc}/simulation_log_dir
 flight-log-dir = $${:etc}/flight_log_dir