Enable nfs protocol (#998)

* vendor: Update prometheus/procfs

Signed-off-by: Hannes Körber <hannes.koerber@haktec.de>

* mountstats: Use new NFS protocol field

In https://github.com/prometheus/procfs/pull/100, the NFSTransportStats
struct was expanded by a field called protocol that specifies the NFS
protocol in use, either "tcp" or "udp". This commit adds the protocol as
a label to all NFS metrics exported via the mountstats collector.

Signed-off-by: Hannes Körber <hannes.koerber@haktec.de>

* Update fixtures for UDP mount

Signed-off-by: Hannes Körber <hannes.koerber@haktec.de>

vendor/github.com/prometheus/procfs/scripts/check_license.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+#
+# Copyright 2018 The Prometheus Authors
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+check_license() {
+  local file=""
+  for file in $(find . -type f -iname '*.go' ! -path './vendor/*'); do
+    head -n3 "${file}" | grep -Eq "(Copyright|generated|GENERATED)" || echo "  ${file}"
+  done
+}
+
+licRes=$(check_license)
+
+if [ -n "${licRes}" ]; then
+  echo "license header checking failed:"
+  echo "${licRes}"
+  exit 255
+fi