Fix session lifetime expectations in SessionWrapper sample code

Summary: By definition, draining the session in the SessionWrapper does not destroy the session. The session is expected to still be alive for a while and be destroyed later. The SessionWrapper should unset itself as the InfoCallback in the destructor.

Reviewed By: hanidamlaj

Differential Revision: D89944465

fbshipit-source-id: def3c151c292b3cc457373d477e2e15f982b71a2

Author: jbeshay

third-party/proxygen/src/proxygen/httpserver/samples/proxy/SessionWrapper.h

@@ -23,6 +23,7 @@ class SessionWrapper : public proxygen::HTTPSession::InfoCallback {
 
   ~SessionWrapper() override {
     if (session_) {
+      session_->setInfoCallback(nullptr);
       session_->drain();
     }
   }