[httpd] Change prototype for the close connection callback

Don't include hreq since it isn't fully valid, so caller shouldn't be invited
to dereference it.

src/httpd.c

@@ -837,7 +837,7 @@ stream_chunk_raw_cb(int fd, short event, void *arg)
 }
 
 static void
-stream_fail_cb(struct httpd_request *hreq, void *arg)
+stream_fail_cb(void *arg)
 {
   struct stream_ctx *st = arg;
 

src/httpd_daap.c

@@ -300,7 +300,7 @@ update_refresh_cb(int fd, short event, void *arg)
 }
 
 static void
-update_fail_cb(struct httpd_request *hreq, void *arg)
+update_fail_cb(void *arg)
 {
   struct daap_update_request *ur = arg;
 

src/httpd_dacp.c

@@ -773,7 +773,7 @@ playstatusupdate_cb(int fd, short what, void *arg)
 }
 
 static void
-update_fail_cb(struct httpd_request *hreq, void *arg)
+update_fail_cb(void *arg)
 {
   struct dacp_update_request *ur = arg;
 

src/httpd_internal.h

@@ -57,7 +57,7 @@ typedef struct httpd_backend_data httpd_backend_data;
 
 typedef char *httpd_uri_path_parts[31];
 typedef void (*httpd_request_cb)(struct httpd_request *hreq, void *arg);
-typedef void (*httpd_close_cb)(struct httpd_request *hreq, void *arg);
+typedef void (*httpd_close_cb)(void *arg);
 typedef void (*httpd_connection_chunkcb)(httpd_connection *conn, void *arg);
 typedef void (*httpd_query_iteratecb)(const char *key, const char *val, void *arg);
 

src/httpd_libevhttp.c

@@ -248,6 +248,9 @@ httpd_request_new(httpd_backend *backend, httpd_server *server, const char *uri,
   return NULL;
 }
 
+// Since this is async, libevent will already have closed the connection, so
+// the parts of hreq that are from httpd_connection will now be invalid e.g.
+// peer_address.
 static void
 closecb_worker(evutil_socket_t fd, short event, void *arg)
 {
@@ -257,7 +260,7 @@ closecb_worker(evutil_socket_t fd, short event, void *arg)
   pthread_mutex_lock(&disconnect->lock);
 
   if (disconnect->cb)
-    disconnect->cb(hreq, disconnect->cbarg);
+    disconnect->cb(disconnect->cbarg);
 
   pthread_mutex_unlock(&disconnect->lock);
 
@@ -289,7 +292,7 @@ closecb_httpd(httpd_connection *conn, void *arg)
   if (!disconnect->cb)
     return;
 
-  disconnect->cb(hreq, disconnect->cbarg);
+  disconnect->cb(disconnect->cbarg);
   httpd_send_reply_end(hreq); // hreq is now deallocated
 }
 

src/httpd_streaming.c

@@ -196,7 +196,7 @@ session_new(struct httpd_request *hreq, bool icy_is_requested)
 /* ----------------------------- Event callbacks ---------------------------- */
 
 static void
-conn_close_cb(struct httpd_request *hreq, void *arg)
+conn_close_cb(void *arg)
 {
   struct streaming_session *session = arg;