s3: Disable keepalive on minio HTTP client

This avoids connections being used for too long and being terminated by the
S3 endpoint.

backend/s3/s3.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"io"
+	"net/http"
 	"strings"
 
 	"github.com/minio/minio-go"
@@ -39,6 +40,11 @@ func Open(cfg Config) (backend.Backend, error) {
 		return nil, err
 	}
 
+	tr := &http.Transport{
+	    DisableKeepAlives: true,
+	}
+	client.SetCustomTransport(tr)
+
 	be := &s3{client: client, bucketname: cfg.Bucket}
 	be.createConnections()