set shutdown title to main window title
set shutdown title to main window title

- this ensures we don't show Bitcoin-Qt as that is still our
  internal application name
- fixes #4427

Rebased-from: 33c62c9c0b25998beb361e6f42e1fd0beebcf05b

litecoin-project/bitcoinomg,litecoin-project/bitcoinomg,litecoin-project/bitcoinomg,litecoin-project/bitcoinomg