Fix update bug in world view
Fix update bug in world view

When the world view updates the scales, it was failing to clear the
respective 'dirty' flag, which would prevent updates from happening
properly. Fix logic by actually clearing the flag when the update
happens.

linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk