HEAD-2156 build-tar-image should respect platform-image in build.spec
HEAD-2156 build-tar-image should respect platform-image in build.spec

kaizengarden/sdc-headnode,kaizengarden/sdc-headnode,numericillustration/sdc-headnode,kaizengarden/sdc-headnode,joyent/sdc-headnode,joyent/sdc-headnode,joyent/sdc-headnode,numericillustration/sdc-headnode,joyent/sdc-headnode,kaizengarden/sdc-headnode,numericillustration/sdc-headnode