Snapmergepuppy: fix for .wh files in pup_rw

Fix for .wh files not being created (in some cases) in pup_rw, described here:
http://woof-ce.26403.n7.nabble.com/Fixing-snapmerge-td240.html#a363

Greetings!
Merge pull request #415 from JakeSFR/testing

snapmergepuppy: fix for .wh files in pup_rw