HTTP authentication fails if QUrl contains password with %

Default for QUrl::password() and QUrl::userName() is in Qt 5.1 QUrl::PrettyDecoded
which means the return value may contain percent-encodings. For authentication
we need the real decoded result, and should instead use QUrl::FullyDecoded.

Note this bug has already been fixed indirectly in Qt 5.2 since the default for the
two methods was changed to QUrl::FullyDecoded.

Change-Id: Ia0f38c073cb001e37ad8b3eda40b3db756bec3dc
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>