AP input events sometimes positioned outside screen geometry

[Gerry Boland]

With MultiMonitor, enable QtMir input debug logging with:
    initctl set-env --global QT_LOGGING_RULES="qtmir.*.debug=true"

Now watch the UI, while running this AP test:

autopilot3 run -v -v unity8.indicators.tests.test_indicators.IndicatorPageTitleMatchesWidgetTestCase.test_indicator_page_title_matches_widget

For the swipe indicators to bottom of the screen, AP outputs:
12:01:25.466 DEBUG _uinput:412 - The pointing 'finger' is now at position 819,1904.
12:01:25.477 DEBUG _uinput:407 - Moving pointing 'finger' to position 819,1914.
12:01:25.479 DEBUG _uinput:412 - The pointing 'finger' is now at position 819,1914.
12:01:25.490 DEBUG _uinput:407 - Moving pointing 'finger' to position 819,1920.
12:01:25.491 DEBUG _uinput:412 - The pointing 'finger' is now at position 819,1920.

while QtMir gets:
qtmir.mir.input: Received MirTouchEvent((id=5,action=change,x=900.219,y=1903.06))
qtmir.mir.input: Sending to Qt (id=5,state=moved,normalPosition=(0.78144,0.991177))
qtmir.mir.input: Received MirTouchEvent((id=5,action=change,x=900.219,y=1916.22))
qtmir.mir.input: Sending to Qt (id=5,state=moved,normalPosition=(0.78144,0.99803))
qtmir.mir.input: Received MirTouchEvent((id=5,action=change,x=900.219,y=1922))
qtmir.mir.input: REJECTING INPUT EVENT, no matching window
qtmir.mir.input: Received MirTouchEvent((id=5,action=up,x=900.219,y=1922))
qtmir.mir.input: REJECTING INPUT EVENT, no matching window

Need to investigate why the values AP request do not match those QtMir prints