Reference include file before exporting $USER

We should check for and pull in the include file before exporting `$USER` in case the user has opted to override the default setting.

contrib/httpuploadcomponent

@@ -20,11 +20,12 @@ CONFIG=/etc/prosody/HttpUploadComponent.yml
 LOGFILE=/var/log/prosody/httpuploadcomponent.log
 PIDFILE=/var/run/${NAME}.pid
 USER=prosody
-export LOGNAME=$USER
 
 # Allow user to override default values listed above
 [ -r /etc/default/$NAME ] && . /etc/default/$NAME
 
+export LOGNAME=$USER
+
 test -x $DAEMON || exit 0
 
 set -e