Fix a fatal error when assert WWW-Authenticate header is sent - Hotfix/5658

Fix a fatal error that occured when an assert[Not]ReponseHeader* method is called to check a MultipleHeaderInterface (like WWW-Authenticate).

When dealing with MultipleHeaderInterface :

* assert* methods will check that at least one header match.
* assertNot* methods will check that every headers doesn't match.

Concerns issue #5658