tests: Do not send multi-line HTTP headers by server

tests: Do not send multi-line HTTP headers by server

cURL 7.83 started to error on multi-line HTTP headers. These headers
were allowed by RFC 2616, but forbidden in RFC 7230. Raising an error is
a bug in cURL. A client must process them.

But it's a bug to produce these headers. A simulated server did so and
simline tests failed on with the affected cURL:

Testing unit: isds_change_password with TOTP
        login: passed
        First phase with invalid password: failed
                reason: Wrong return code: expected=Not logged in, returned=Network problem (http://[::1]:39409/asws/changePassword: Weird
server reply)

This patch changes the multi-line headers into a single-line header.
This is not accurate because the new-lines could be Base64 encoded, but
it's a good approximation considering the server does not yet support
RFC 2047 encoding.

https://github.com/curl/curl/issues/8844