Avoid advertising NTLM if it isn't technically supported
Avoid advertising NTLM if it isn't technically supported

This lets browsers to fall back to basic auth if supported
(similar to 4e7967e797e5c8912a67c0de8f172bb95b5172ff).

Add boolean param to is_mech_allowed which denotes whether
the caller supports multiple step.

Reviewed-by: Simo Sorce <65f99581a93cf30dafc32b5c178edc6b0294a07f@redhat.com>

davisd123/mod_auth_gssapi,davisd123/mod_auth_gssapi,frenche/mod_auth_gssapi,frenche/mod_auth_gssapi,devurandom/mod_auth_gssapi,devurandom/mod_auth_gssapi,frenche/mod_auth_gssapi,uhd-urz/mod_auth_gssapi,uhd-urz/mod_auth_gssapi,frenche/mod_auth_gssapi,davisd123/mod_auth_gssapi,devurandom/mod_auth_gssapi,uhd-urz/mod_auth_gssapi