Add a 5 seconds of timeouts to connect to S3.

The default is 1000ms, but we can hit it a lot of we don't have direct
link to AWS (e.g. using VPN).

src/libstore/s3-binary-cache-store.cc

@@ -126,6 +126,7 @@ ref<Aws::Client::ClientConfiguration> S3Helper::makeConfig(const string & region
         res->endpointOverride = endpoint;
     }
     res->requestTimeoutMs = 600 * 1000;
+    res->connectTimeoutMs = 5 * 1000;
     res->retryStrategy = std::make_shared<RetryStrategy>();
     res->caFile = settings.caFile;
     return res;