varlink: address some trivial points Claude found

Just addressing Claude's last review from #41815

src/libsystemd/sd-varlink/varlink-util.c

@@ -335,7 +335,7 @@ ssize_t varlink_execute_directory(
 
                 r = sd_varlink_set_relative_timeout(link, timeout_usec);
                 if (r < 0)
-                        return r;
+                        return log_debug_errno(r, "Failed to set relative timeout: %m");
 
                 if (more)
                         r = sd_varlink_observe(link, method, parameters);

src/test/test-varlink.c

@@ -1009,7 +1009,7 @@ TEST(execute_directory) {
                                      /* timeout_usec= */ USEC_INFINITY,
                                      execute_dir_reply,
                                      &reply_count), (ssize_t) ELEMENTSOF(names));
-        ASSERT_EQ(reply_count, (unsigned) ELEMENTSOF(names));
+        ASSERT_EQ(reply_count, ELEMENTSOF(names));
 
         FOREACH_ELEMENT(eds, servers) {
                 ASSERT_OK(-pthread_join(eds->thread, NULL));