### What changes were proposed in this pull request?
Add helm chart unit tests.
### Why are the changes needed?
Unit tests can make resource manifests are rendered as expected with various configurations.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Detailed information about how to run helm chart unit tests can be found here [helm-unittest/helm-unittest](https://github.com/helm-unittest/helm-unittest). First, you need to install helm unit test plugin:
```shell
helm plugin install https://github.com/helm-unittest/helm-unittest.git
```
Then, run helm chart unitt tests as follows:
```shell
$ helm unittest charts/celeborn --file "tests/**/*_test.yaml" --strict --debug
load_plugins.go:110: [info] file (/Users/chenyi/Library/helm/plugins/helm-acr/completion.yaml) not provided by plugin. No plugin auto-completion possible
### Chart [ celeborn ] charts/celeborn
PASS Test Celeborn configmap charts/celeborn/tests/configmap_test.yaml
PASS Test Celeborn master pod monitor charts/celeborn/tests/master/podmonitor_test.yaml
PASS Test Celeborn master priority class charts/celeborn/tests/master/priorityclass_test.yaml
PASS Test Celeborn master service charts/celeborn/tests/master/service_test.yaml
PASS Test Celeborn master statefulset charts/celeborn/tests/master/statefulset_test.yaml
PASS Test Celeborn worker pod monitor charts/celeborn/tests/worker/podmonitor_test.yaml
PASS Test Celeborn worker priority class charts/celeborn/tests/worker/priorityclass_test.yaml
PASS Test Celeborn worker service charts/celeborn/tests/worker/service_test.yaml
PASS Test Celeborn worker statefulset charts/celeborn/tests/worker/statefulset_test.yaml
Charts: 1 passed, 1 total
Test Suites: 9 passed, 9 total
Tests: 48 passed, 48 total
Snapshot: 0 passed, 0 total
Time: 183.011375ms
```
Closes#2511 from ChenYi015/helm-unittest.
Authored-by: Yi Chen <github@chenyicn.net>
Signed-off-by: Cheng Pan <chengpan@apache.org>
