ntlm-test-helper: fix

ntlm-test-helper: fix

We need to set SOUP_NTLM_AUTH_DEBUG to an empty string (to tell
SoupAuthNTLM to always use built-in NTLM), not leave it unset, which
will let SoupAuthNTLM use the real ntlm_auth binary.

(The effect of this bug was that instead of always using built-in
NTLM, ntlm-test-helper would first try to use ntlm_auth, and fail
because there were no cached credentials, and then fall back to
built-in NTLM, which meant that we were testing the fallback codepath
even in the supposed-to-be-non-fallback case. Unless your username was
"alice" or "bob" and you had a working winbind configuration, in which
case the tests would just fail.)

Also, fix up ntlm-test a bit, so that if ntlm-test-helper for some
reason tries to authenticate as someone other than alice or bob, it
recognizes this, rather than considering everyone who isn't alice to
be bob.