[partition] Preserve desired partition flags

- Use the desired (future) flags, if set, to initialize the
   flags checkboxes. If there are no future flags set, this
   returns active flags as before.
 - This fixes the situation where editing a partition, changing
   flags, then editing it *again* re-starts with the original
   flags instead of the modified flags.

src/modules/partition/gui/EditExistingPartitionDialog.cpp

@@ -141,7 +141,7 @@ EditExistingPartitionDialog::setupFlagsList()
             m_ui->m_listFlags->addItem( item );
             item->setFlags( Qt::ItemIsUserCheckable | Qt::ItemIsEnabled );
             item->setData( Qt::UserRole, f );
-            item->setCheckState( ( m_partition->activeFlags() & f ) ?
+            item->setCheckState( ( PartitionInfo::flags( m_partition ) & f ) ?
                                      Qt::Checked :
                                      Qt::Unchecked );
         }