qadd Select / deselect all not working correctly

[Robert Ladyman]

On launch, Select-all has non-versioned files correctly checked.

Unticking Seleect-all correctly deselects the files on first display, but subsequent toggling does not unless the list of files is clicked upon or clicking outside the window.

Selecting just one non-versioned file does not uncheck the 'Select / deselect' box: in fact it sets it. Unchecking select all at this point then checks all unversioned files, incorrectly. Again, clicking in the list of files (or outside the window) corrects this.
However, if the select all is left ticked, clicking outside the window (or in the list of files) selects all the non-versioned files.

See also https://bugs.launchpad.net/qbrz/+bug/2054796

[Robert Ladyman (saccadic-masking)]

This behaviour is also causing a similar failure in test_commit_selectall() (in test_treewidget.py)