Allow copy of dead symbolic links

see https://dev.cfengine.com/issues/6175. 
Please review carefully.

This needed due to the upgrade from 3.3. to 3.6 and this functionality is required.
Use fewer parentheses !
Also, the whole `else { if (cond) { block; } else {block;} }` structure can lose a layer of braces and level of indentation as `else if (cond) { block; } else { block; }`.