Update vendored github.com/prometheus/procfs packages

vendor/github.com/prometheus/procfs/proc.go

@@ -1,6 +1,20 @@
+// 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.
+
 package procfs
 
 import (
+	"bytes"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -113,7 +127,7 @@ func (p Proc) CmdLine() ([]string, error) {
 		return []string{}, nil
 	}
 
-	return strings.Split(string(data[:len(data)-1]), string(byte(0))), nil
+	return strings.Split(string(bytes.TrimRight(data, string("\x00"))), string(byte(0))), nil
 }
 
 // Comm returns the command name of a process.