Automatic merge from submit-queue

build: fixed ${KUBE_ROOT} prefix for build scripts

Running `./make-build-image.sh` command inside the `build` directory doesn't work:

```sh
$ cd build
$ ./make-build-image.sh 
./../build/common.sh: line 32: hack/lib/init.sh: No such file or directory
```

This PR adds `${KUBE_ROOT}` prefix for the `source` bash function. Also I added braces to unify the code style.

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