Was caused by the bump node not being evaluated because the other branch
was evaluated before.
To fix this, we use fromnode instead of tonode.
Also we fix a potential issue with recursiveness because
ntree_shader_copy_branch() also use nodeChainIterBackwards() which would
reset the iter_flag in the middle of the parent iteration. Use iter_flag
as a bitflag for each iteration to fix this.
f61a8a2abd