fix failure of non-regression test SMESH_TEST/Grids/smesh/mesh_Projection_2D/A1

fix failure of non-regression test SMESH_TEST/Grids/smesh/mesh_Projection_2D/A1

 Let the helper set nodes on shape to avoid the pb with a medium nodes
 set by mistake to EDGE instead of FACE.
 The case is a triangle whose 3 nodes are on the same EDGE. The worst
 is that in this case the medium node which is logically on FACE falls
 to a straight EDGE, as the triangle is of zero area.