Add snowmix wrapper to handle graceful shutdown

Dockerfile

@@ -36,4 +36,4 @@ RUN mkdir $GOPATH && cd /tools/de-ip-hdmi && go get -d . && go build . && chmod
 RUN sed -i -e 's_NC\=.*_NC="nc -q1"_' /usr/local/lib/Snowmix-0.5.1/scripts/snowmix-settings
 
 USER snowmix
-CMD snowmix
+CMD [ "/tools/run-snowmix" ]

tools/run-snowmix

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# Just a simple wrapper around snowmix, so that SIGTERM will make it shutdown
+# gracefully
+
+term_handler() {
+    echo 'quit' | nc -q1 127.0.0.1 9999
+}
+
+trap 'term_handler' SIGTERM
+
+snowmix & wait ${!}
+exit $?