Fix units ignoring range when attacking in one case, and fix targeting formations

Fixes for rP22425:

• units could occasionally ignore range checks when attacking.
• attacking a formation wouldn't pick new targets correctly.

While testing, I also think the walk then walk and fight behaviour should be changed to just walk and fight or units might just run towards enemies and not attack them, which looks rather odd.

Reported By: Angen

Fixes #5530

Differential Revision: https://code.wildfiregames.com/D2119