Fixed content type check in login_password
    
    login_password is expecting that request content_type will be 'application/x-www-form-urlencoded'.
    
    Current check is an equality check of content_type http header.
    
    RFC 3875 defines that content type can contain parameters separated by ';'. For example: when firefox is doing ajax call it sets the request header to 'application/x-www-form-urlencoded; charset=UTF-8' which leads to negative result.
    
    This patch makes the check more benevolent to allow such values.
    
    Patch is a fixup for:
    https://fedorahosted.org/freeipa/ticket/2095