fix failure to umount union/ in tests by sleeping a little
fix failure to umount union/ in tests by sleeping a little

yogoloth/unionfs-fuse,kissthink/unionfs-fuse-1,evnu/unionfs-fuse,evnu/unionfs-fuse,kissthink/unionfs-fuse-1,evnu/unionfs-fuse,yogoloth/unionfs-fuse,kissthink/unionfs-fuse-1,yogoloth/unionfs-fuse