Run test and not just subtests parallely

[kislaykishore]

Description

• Calling t.Parallel() in the subtests just invokes the subtest concurrently with other subtest for the same test but those subtests will not be interleaved with other tests in the same package. Fix that to run subtests parallely with other tests in the same package.
• Fix races in tests.

Link to the issue in case of a bug fix.

NA

Testing details

1. Manual - NA
2. Unit tests - NA
3. Integration tests - NA

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 71.95%. Comparing base (dd1542d) to head (ea17c3f).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2071 +/- ## ======================================= Coverage 71.95% 71.95% ======================================= Files 99 99 Lines 10870 10870 ======================================= Hits 7822 7822 Misses 2715 2715 Partials 333 333 ``` | [Flag](https://app.codecov.io/gh/GoogleCloudPlatform/gcsfuse/pull/2071/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/GoogleCloudPlatform/gcsfuse/pull/2071/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | `71.95% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform#carryforward-flags-in-the-pull-request-comment) to find out more.

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