Stop swallowing stdout and stderr when we check for the staging bucket.

Should help debug #23461

cluster/gce/util.sh

@@ -224,7 +224,7 @@ function upload-server-tars() {
     local staging_bucket="gs://kubernetes-staging-${project_hash}${suffix}"
 
     # Ensure the buckets are created
-    if ! gsutil ls "${staging_bucket}" > /dev/null 2>&1 ; then
+    if ! gsutil ls "${staging_bucket}" ; then
       echo "Creating ${staging_bucket}"
       gsutil mb -l "${region}" "${staging_bucket}"
     fi