emission shader casting shadows - problem not solved There is already a post about it in here, but the problem is not solved, in fact it is not a solution to the problem. What can we do to avoid shadows from emission shaders?  

There's a similar post about it in here, and still the problem is not solved, and it seems: LIGHT PATHS CANNOT BE USED FOR MESH LIGHTS.
Here is a blend file that contains a simple experiment that demonstrates that the aforementioned solution in the first link does not work:


So, how do we avoid mesh lights to cast shadows?
In your particular example case you could replace your emitter object with an area lamp - this does support suppressing shadows as shown :

3d View :


Cast Shadow disabled :


Cast Shadow enabled :


However, I don't think it's possible to suppress shadows from mesh-based emission materials due to the nature of the physics based rendering. ie, if you're suppressing light from emission surfaces then what about light reflected from a glossy surface - that could also cast shadows - as could light from a diffuse surface (albeit much more subtle, but it would still be a shadow).