Prevent multiple instances of username entry dialog from running

src/freedombone-image-customise

     echo '' >> $START_DESKTOP
     echo 'INITIAL_TOX_USERNAME=""' >> $START_DESKTOP
     echo 'while [ ${#INITIAL_TOX_USERNAME} -eq 0 ]; do' >> $START_DESKTOP
+    echo '  username_dialog_count=$(ps aux | grep zenity | wc -l)' >> $START_DESKTOP
+    echo '  if [ $username_dialog_count -gt 1 ]; then' >> $START_DESKTOP
+    echo '    exit 0' >> $START_DESKTOP
+    echo '  fi' >> $START_DESKTOP
     echo "  data=\$(zenity --forms --title=\"$MESH_TITLE\" --text=\"$MESH_SET_USERNAME\" --separator=\",\" --add-entry=\"Username\")" >> $START_DESKTOP
     echo '  accepted=$?' >> $START_DESKTOP
     echo '  if ((accepted == 0)); then' >> $START_DESKTOP