[WIP] PIM-3207: Apply the current channel in the edit product page

Problem: 
 * go the product grid, change the channel and edit the product
 * the current channel is set on the scopable fields
 * back to the grid, and edit another product
 * the current channel is applied 2 times on the scopable fields
 * back to the grid, and edit another product
 * the current channel is applied 3 times on the scopable fields
 * etc..