[cleanup] Add a condition on Session open status

Add a condition on Session open status to avoid access model from UI
thread if the session is closed

Change-Id: I458212926f3a210cae8539c699ab87a1934c070a
Signed-off-by: Esteban Dugueperoux <esteban.dugueperoux@obeo.fr>
[437528] Fix wrong rectilinear computation.

* We do not convert to rectilinear edges that are already rectilinear.
* If an edge is rectilinear with more than 2 bendpoints, we created 2
additional bendpoints by mistake. This treatment is supposed to be for
straight edge converted to rectilinear.
* Avoid index out of bound in the case of edge with less than two
bendpoints.
* Add a new SWTBot test.

Bug: 437528
Change-Id: I4554aa86d1f252c6e985edcf3919afcf877e4471
Signed-off-by: Florian Barbin <florian.barbin@obeo.fr>
[437528] Handle edge centering during the repair action.

* If the edge centering property has been updated within the VSM and the
user has launched a repair on aird file (without open or launch any
refresh on
representations), the EdgeStyle centered property was well updated but
the GMF edge bendpoints were not.

Bug: 437528
Change-Id: I0dc3b24beb0540fd7406d25e05bfc7fb8425a5d2
Signed-off-by: Florian Barbin <florian.barbin@obeo.fr>
[test] Make HideRevealDiagramElementsLabelsTest more reliable

Change-Id: If999fa27b97500e789f8b99ccbf0298077a5a3d2
Signed-off-by: Laurent Redor <laurent.redor@obeo.fr>