BlackBerry: Fix QFileDialog show()/hide()

QFileDialog::show() no longer worked after the dialog had already been shown
and hidden before.

Task-number: QTBUG-34983
Change-Id: I7300374b74805308e0966db7b3545e5fd8470465
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
BlackBerry: remove unused variable

m_result is not used by qqnxfiledialoghelper_bb10.cpp, only by its playbook
counterpart.

Change-Id: I4fae924283560703393c5313527c5c9c2005d35b
Reviewed-by: Tobias Koenig <tobias.koenig.qnx@kdab.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
BlackBerry: properly clean up QFileDialog files

Task-number: QTBUG-34983

Change-Id: I1af5c6a9c43eba77394b11d31d1d223af8bc221f
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>