Disable connection-bound for basic-auth

Clients don't expect this and therefore might inappropriately reuse the
connection for another user identity (with or without creds).

This is currently more of an issue due to issue 22, example:
curl -v http://myhost/ -u usera:passa --next http://myhost/ -u userb:passb

Closes #36

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