Azure: Use default HTTP transport

internal/backend/azure/azure.go

@@ -3,6 +3,7 @@ package azure
 import (
 	"context"
 	"io"
+	"net/http"
 	"os"
 	"path"
 	"strings"
@@ -35,6 +36,8 @@ func open(cfg Config) (*Backend, error) {
 		return nil, errors.Wrap(err, "NewBasicClient")
 	}
 
+	client.HTTPClient = &http.Client{Transport: backend.Transport()}
+
 	service := client.GetBlobService()
 
 	sem, err := backend.NewSemaphore(cfg.Connections)