Fix datadir handling in bitcoin-qt
Fix datadir handling in bitcoin-qt

This prevents premature tries to access or create the default datadir.
This is useful when the -datadir option is specified and the default
datadir is unreachable.

DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,peercoin/peercoin,peercoin/peercoin,peercoin/peercoin,DigitalPandacoin/pandacoin,peercoin/peercoin,peercoin/peercoin,DigitalPandacoin/pandacoin,peercoin/peercoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin