[upgrade test]Fix issues when the image path is not url

[nhe-NV]

When the image path is not url, it will fail to download image. need to support the save_as as previously

Description of PR

Summary: When the image path is not url, it will fail to download image. need to support the save_as as previously Fixes # (issue)

Type of change

• [x] Bug fix
• [ ] Testbed and Framework(new/improvement)
• [ ] Test case(new/improvement)

Back port request

• [ ] 201911
• [ ] 202012
• [ ] 202205
• [x] 202305
• [x] 202311

Approach

What is the motivation for this PR?

How did you do it?

if the image is downloaded already before run the reduce_and_add_sonic_images.py, use the downloaded image.

How did you verify/test it?

After the fix, run the test case with image path specified as not url format, test could pass

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

[liat-grozovik]

@yxieca can you please help to merge or assign someone to review?