Refactor fragile msg macro W and W2 to not burry return control flow.

Refactor fragile msg macro W and W2 to not burry return control flow.

Instead, have them accept and assign a return paramter leaving
the return control flow up to the caller.  Clean up otherwise
misleading returns present even after "NOT REACHED" comments.

Change-Id: I0861921f73ab65d55b95eabd27514f0129152723
Signed-off-by: Jon Loeliger <jdl@netgate.com>