Blender Git Loki

Fix T87356 & T87358: Small multi-input socket issues

T87356 occured because last_node_hovered_while_dragging_a_link was not
set on node_link_init.
The assert in T87358 failed because the sorting operation was called even
if the drag link contained a link to another socket.
A little one frame jump was caused because frame was refreshed after
picking a link and before sorting happened.

Reviewer: Hans Goudey

Differential Revision: https://developer.blender.org/D10940