[yocto] kernel defconfig configuration

[Edward Wingate]

I created a linux-wandboard_3.14.28.bbappend that just specifies a new
defconfig.  I see my defconfig being used to generate a .config.  But
then something renames .config to .config.old and replaces it with
another .config that no longer has the configurations I want.  I can't
find what is doing the override.  This is the run.do_configure:
http://pastebin.com/zPfuSwTV.  Can anyone suggest where to look next?
Thanks for any help.