cgpt: inherit any new keys defined in child config.

In my CL to re-work cgpt, I broke hybrid_mbr usage with parent
configs as I didn't inherit all keys from the new config. This
fixes that by making the .setdefault inheritance generic.

BUG=chromium:334916
TEST=Tested and checked that beaglebone config had hybrid_mbr=True
and all other fields looked correct for the legacy json file.

Change-Id: I238938583ce13d5f8bf7cf99073278be054b6124
Reviewed-on: https://chromium-review.googlesource.com/185954
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Queue: Chris Sosa <sosa@chromium.org>
Tested-by: Chris Sosa <sosa@chromium.org>
1 file changed