lb/ForwardHttpRequest: use class FailurePtr
lb/ForwardHttpRequest: use class FailurePtr

Similar to commit 8f33224c3b901544a4dd6b13db0ce0d6524b1fef

CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy