Set dyno type on startup

Using the provided $DYNO environment variable, parse out the significant
portion and append it to the end of the Agent config file.

This will allow metrics selection per running dyno (dyno_tpe:web vs
dyno_type:worker).

extra/run-dogstatsd.sh

@@ -19,6 +19,12 @@ else
   exit 1
 fi
 
+# Set dyno type as a Datadog tag
+DYNOTYPE=$(echo $DYNO|cut -f1 -d'.')
+DYNOTAG=dyno_type:$DYNOTYPE
+
+echo "tags: $DYNOTAG" >> /app/.apt/opt/datadog-agent/agent/datadog.conf
+
 (
   # Unset other PYTHONPATH/PYTHONHOME variables before we start
   unset PYTHONHOME PYTHONPATH