res_pjsip_session.c: Prevent use-after-free with TEST_FRAMEWORK enabled

We need to copy the endpoint name before we call ao2_cleanup() on it,
otherwise we might try to access memory that has been reclaimed.

ASTERISK-28445 #close
Reported by: Bernhard Schmidt

Change-Id: I404b952608aa606e0babd3c4108346721fb726b3

res/res_pjsip_session.c

@@ -1315,8 +1315,10 @@ static void session_destructor(void *obj)
 	struct ast_sip_session *session = obj;
 	struct ast_sip_session_supplement *supplement;
 	struct ast_sip_session_delayed_request *delay;
+
+	/* We dup the endpoint ID in case the endpoint gets freed out from under us */
 	const char *endpoint_name = session->endpoint ?
-		ast_sorcery_object_get_id(session->endpoint) : "<none>";
+		ast_strdupa(ast_sorcery_object_get_id(session->endpoint)) : "<none>";
 
 	ast_debug(3, "Destroying SIP session with endpoint %s\n", endpoint_name);