GCS: fix the WithoutAuthentication option

[haoxins]

What type of PR is this?

• [x] bug
• [ ] feature
• [ ] enhancement

What problem(s) does this PR solve?

When you run the application in the GCP ENVs, such as GKE or GCE. The GCS client will try to get credentials underlying the ENVs.

See https://cloud.google.com/kubernetes-engine/docs/concepts/workload-identity

Unless the user specifies that, we shouldn't set the WithoutAuthentication option.

How do you solve it?

Special notes for your reviewer, ex. impact of this fix, design document, etc:

[veezhang]

@haoxins Thanks! Can you fix the testing ? BTW, do you know which env has the effect?

[haoxins]

I need to find a solution to fix the test. The test failed because it is not running on the GKE/GCE environment.

https://cloud.google.com/docs/authentication/application-default-credentials?hl=zh-cn#attached-sa

[veezhang]

@haoxins Setting WithoutAuthentication to true may solve the problem.

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (1cbec84) 87.89% compared to head (feb24d8) 87.89%.

:exclamation: Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #290 +/- ## ======================================= Coverage 87.89% 87.89% ======================================= Files 79 79 Lines 3857 3857 ======================================= Hits 3390 3390 Misses 458 458 Partials 9 9 ``` | [Files Changed](https://app.codecov.io/gh/vesoft-inc/nebula-importer/pull/290?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vesoft-inc) | Coverage Δ | | |---|---|---| | [pkg/source/gcs.go](https://app.codecov.io/gh/vesoft-inc/nebula-importer/pull/290?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vesoft-inc#diff-cGtnL3NvdXJjZS9nY3MuZ28=) | `85.00% <100.00%> (ø)` | |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[haoxins]

@haoxins Setting WithoutAuthentication to true may solve the problem.

fixed

[veezhang]

@haoxins Thanks a lot!