MINOR: session: do not send an HTTP/500 error on SSL sockets

If a session fails its initialization, we don't want to send HTTP/500
over the socket if it's not a raw data layer.
diff --git a/src/session.c b/src/session.c
index 0f7a9ba..4503b41 100644
--- a/src/session.c
+++ b/src/session.c
@@ -33,6 +33,7 @@
 #include <proto/frontend.h>
 #include <proto/hdr_idx.h>
 #include <proto/log.h>
+#include <proto/raw_sock.h>
 #include <proto/session.h>
 #include <proto/pipe.h>
 #include <proto/protocols.h>
@@ -185,7 +186,7 @@
 		session_store_counters(s);
 	pool_free2(pool2_session, s);
  out_close:
-	if (ret < 0 && p->mode == PR_MODE_HTTP) {
+	if (ret < 0 && l->data == &raw_sock && p->mode == PR_MODE_HTTP) {
 		/* critical error, no more memory, try to emit a 500 response */
 		struct chunk *err_msg = http_error_message(s, HTTP_ERR_500);
 		send(cfd, err_msg->str, err_msg->len, MSG_DONTWAIT|MSG_NOSIGNAL);