fix: correct STORAGE_EMULATOR_HOST handling (#2069, #1314)

[mgabeler-lee-6rs]

credit to @jpambrun for identifying the fix

Test assertions needed to change slightly since they were asserting the
presence of functionality that doesn't actually work, specifically allowing
one to change the base url to not have /storage/v1. The code fundamentally
does not support this at all, and is full of places that are hard coded to
always include that path element. The code does support having a base path
before that however, and so that is what I updated the tests to check.

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #1314
Fixes #2069

[danielbankhead]

Looks good - one minor, optional suggestion.

We have a code freeze for the next few weeks - will merge this after 🙂