First free factory inconsistently getting default priority from nanoframe priority instead of constructor priority.

[Stuart1998]

I haven't been able to determine what exactly causes this because it's inconsistent, but designated default priority for your first factory is sometimes ignored for indeterminate reasons, causing factories that should be plopped at low priority to spawn at medium priority instead.

EDIT: Apparently, when default constructor priority is ignored it's getting the priority from the nanoframe priority instead.

[Mach565]

See also #4898