Look for resources nigh the order when forced.

When tasked to gather, entities looked for resources close to their current location when the target was invalid (e.g. full).
Now on forced orders the entities will look for resources close to that order's location, when possible.

Differential revision: https://code.wildfiregames.com/D4146
Fixes: #6085
Reviewed by: @Imarok
Tested by: @Langbart
Comments by: @marder, @Stan, @wraitii