Shore up the implementation of copyfile_sparse
Shore up the implementation of copyfile_sparse

Signed-off-by: Chris Lalancette <281cd07d7578d97c83271fbbf2faddb83ab3791c@gmail.com>

imcleod/oz,NeilBryant/oz,clalancette/oz,imcleod/oz,mgagne/oz,cernops/oz,cernops/oz,ndonegan/oz,clalancette/oz,NeilBryant/oz,ndonegan/oz,nullr0ute/oz,nullr0ute/oz,moofrank/oz,mgagne/oz,moofrank/oz