[main][cherry-pick] Fix(curl): surface auth errors and avoid panic on nil HTTP response - #3839

MakeCurlRequest assumed that a non-nil error always came with an HTTP
response (e.g. a 4xx/5xx from the API). That assumption breaks when the
request fails before reaching the API — for example a token refresh /
client-credentials authentication failure in the UAA request wrapper,
which returns an error with a nil *http.Response.

In that case:
- Without --fail, the error was swallowed and cf curl printed empty
  output, giving the user no indication anything went wrong.
- With --fail, the code dereferenced httpResponse.StatusCode on the nil
  response and panicked.

Only surface CurlExit22Error when an HTTP response is actually present;
when the response is nil, return the underlying error directly so the
user sees a real message (e.g. "Bad credentials") and cf curl exits
cleanly instead of panicking. Existing behavior for real HTTP error
responses (print body by default, fail only with --fail) is unchanged.

Signed-off-by: Prem Kumar Kalle <prem.kalle@broadcom.com>