ProxyFix support IPv6 Addressing
    
    Use rsplit() to split host/port, this will work for both
    IPv4, IPV6 and hostnames. Only rsplit() if ':' in string
    and the string does not end with closing bracket.
    
    Upstream: https://github.com/pallets/werkzeug/pull/2263
    Related-to: https://review.rdoproject.org/r/q/I34f65f12bbbab073233eb9320fba5eb1044d9127