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fix error when run release.sh not in {KUBE_ROOT}

**What this PR does / why we need it**:
add `${KUBE_ROOT}/` in directory, otherwise run 
```shell
cd kubernetes/build  
./release.sh
```
will exit:
```shell
+++ [0112 18:18:48] Verifying Prerequisites....
cp: cannot stat ‘build/build-image/Dockerfile’: No such file or directory
!!! [0112 18:18:48] Call tree:
!!! [0112 18:18:48]  1: ./release.sh:35 kube::build::build_image(...)
!!! Error in ./../build/common.sh:454
  Error in ./../build/common.sh:454. '((i<3-1))' exited with status 1
Call stack:
  1: ./../build/common.sh:454 kube::build::build_image(...)
  2: ./release.sh:35 main(...)
Exiting with status 1
```

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```