fix(start): remove stale supervisor configuration files on start

Repeated start might have existing files around.

Fixes WeblateOrg#2579

start

@@ -201,6 +201,8 @@ if [ "$1" = "runserver" ] ; then
     # Select which services to run
     SUPERVISOR_CONF=/run/supervisor.conf.d/
     mkdir -p "$SUPERVISOR_CONF"
+    # Remove possible stale files from previous start
+    rm -f "$SUPERVISOR_CONF/*"
     if [ -n "$WEBLATE_SERVICE" ] ; then
         if [ "$WEBLATE_SERVICE" != "celery-beat" ] ; then
             DO_MIGRATE=0