Fix of setHttpDebugLog function

[Two-Hearts]

What is not working as expected?

Creating an issue to track these comments:
#827 (comment)
#827 (comment)

What did you expect to happen?

Quote from @shizhMSFT: When authClient.Client is nil, http.DefaultClient.Transport is changed to http.DefaultTransport if it is nil. Later, http.DefaultClient.Transport is changed to NewTransport. That's a global change and should be avoided.

How can we reproduce it?

nil

Describe your environment

all environments

What is the version of your Notation CLI or Notation Library?

current main branch