Adds comment to explain startup script switch

docker_config_files/client/grr_fleetspeak_client.sh

@@ -1,4 +1,10 @@
 #!/bin/bash
+#
+# This script is run when Fleetspeak runs the GRR client.
+# It first checks whether we run Docker Compose Watch (i.e. in dev mode).
+#   If so we run the grr_fleetspeak_client python script so Docker Compose can
+#   swap in the source code updates on a continuous basis.
+#   If not we run grrd as we would do so in production.
 if [ -f /usr/share/grr-server/bin/grr_fleetspeak_client ]; then
   /usr/share/grr-server/bin/python /usr/share/grr-server/bin/grr_fleetspeak_client "$@"
 else