vsp change device_model method

[tanjiangyu-ghca]

What this PR does / why we need it:

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

Special notes for your reviewer:

Release note:

[codecov[bot]]

Codecov Report

Merging #933 (d25b919) into master (996ff13) will increase coverage by 0.00%. The diff coverage is 57.14%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #933 +/- ## ======================================= Coverage 71.51% 71.51% ======================================= Files 181 181 Lines 21925 21925 Branches 3333 3333 ======================================= + Hits 15679 15680 +1 - Misses 5175 5176 +1 + Partials 1071 1069 -2 ``` | [Impacted Files](https://codecov.io/gh/sodafoundation/delfin/pull/933?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sodafoundation) | Coverage Δ | | |---|---|---| | [delfin/drivers/hitachi/vsp/rest\_handler.py](https://codecov.io/gh/sodafoundation/delfin/pull/933/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sodafoundation#diff-ZGVsZmluL2RyaXZlcnMvaGl0YWNoaS92c3AvcmVzdF9oYW5kbGVyLnB5) | `39.39% <57.14%> (-1.02%)` | :arrow_down: | | [delfin/drivers/fake\_storage/\_\_init\_\_.py](https://codecov.io/gh/sodafoundation/delfin/pull/933/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sodafoundation#diff-ZGVsZmluL2RyaXZlcnMvZmFrZV9zdG9yYWdlL19faW5pdF9fLnB5) | `95.17% <0.00%> (+0.76%)` | :arrow_up: |