services/obs: Service test failed for content mismatch

[Xuanwo]

• Related PR: https://github.com/beyondstorage/go-storage/pull/957
• Test Case: https://github.com/beyondstorage/go-storage/runs/3982686814?check_suite_focus=true

     When Read a file with offset or size 
      When Read with offset 
        The error should be nil ✔✔
        The content should be match ✔✘✔
      When Read with size 
        The error should be nil ✔✔
        The content should be match ✔✘✔
      When Read with offset and size 
        The error should be nil ✔✔
        The content should be match ✔✘✔

 Failures:

  * /data/actions/beta/go-storage/go-storage/services/obs/tests/storage_test.go 
  Line 14:
  Expected: '138112'
  Actual:   '451281'
  (Should be equal)

  * /data/actions/beta/go-storage/go-storage/services/obs/tests/storage_test.go 
  Line 14:
  Expected: '1288953'
  Actual:   '2688928'
  (Should be equal)

  * /data/actions/beta/go-storage/go-storage/services/obs/tests/storage_test.go 
  Line 14:
  Expected: '49793'
  Actual:   '291284'
  (Should be equal)

Obs implementation must be buggy, let's fix it before release.

[Xuanwo]

obs doesn't support offset and size now:

https://github.com/beyondstorage/go-storage/blob/9aa9a15f09f50d75272d28793716bf6a16571e4b/services/obs/storage.go#L185-L202

this can be fixed by like:

https://github.com/beyondstorage/go-storage/blob/9aa9a15f09f50d75272d28793716bf6a16571e4b/services/bos/storage.go#L181-L193

[Xuanwo]

Wait for https://github.com/huaweicloud/huaweicloud-sdk-go-obs/issues/10