lmtp: Die at startup if config reading fails.

Although most of the time it's not strictly required for config to be read here,
one exception is SSL server settings. If this config reading fails, the SSL
initialization just crashes. So this gives a better error message than a crash.
Also config reading really isn't supposed to fail anyway.

src/lmtp/main.c

@@ -50,8 +50,9 @@ static void drop_privileges(void)
 	i_zero(&input);
 	input.module = "lmtp";
 	input.service = "lmtp";
-	(void)master_service_settings_read(master_service,
-					   &input, &output, &error);
+	if (master_service_settings_read(master_service,
+					 &input, &output, &error) < 0)
+		i_fatal("Error reading configuration: %s", error);
 	restrict_access_by_env(NULL, FALSE);
 }