chore(acceptance): fix the issue 'HW_SFS_FILE_SYSTEM_NAMES' is empty

[wuzhuanhong]

What this PR does / why we need it:
The result of strings.Split("", ",") is []string{""}, so its length is 1，so it does not meet the given judgment condition.

Which issue this PR fixes:
(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)
fixes #xxx

Special notes for your reviewer:

Release note:

PR Checklist

• Tests added/passed.

make testacc TEST='./huaweicloud' TESTARGS='-run=TestAccSomethingV0_basic'
...
=== RUN   TestAccSomethingV0_basic
--- PASS: TestAccSomethingV0_basic (70.75s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud       70.796s

• Documentation updated.

• Schema updated.

• CheckDeleted.

  • a. During query operation (Read Context)
    aa. Resource not found
    >>>>>> Paste the screenshot here <<<<<<

  • b. During delete/disassociate/unbind operation (Delete Context)
    ba. Resource not found
    >>>>>> Paste the screenshot here <<<<<<

[Lance52259]

/approve
/lgtm

[github-ci-robot]

This PR has been approved by: @Lance52259

/approve
/lgtm