Update libkv dependency

vendor/google.golang.org/grpc/credentials/credentials.go

@@ -1,33 +1,18 @@
 /*
  *
- * Copyright 2014, Google Inc.
- * All rights reserved.
+ * Copyright 2014 gRPC authors.
  *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
+ * 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
  *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
+ *     http://www.apache.org/licenses/LICENSE-2.0
  *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * 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.
  *
  */
 
@@ -102,6 +87,10 @@ type TransportCredentials interface {
 	// authentication protocol on rawConn for clients. It returns the authenticated
 	// connection and the corresponding auth information about the connection.
 	// Implementations must use the provided context to implement timely cancellation.
+	// gRPC will try to reconnect if the error returned is a temporary error
+	// (io.EOF, context.DeadlineExceeded or err.Temporary() == true).
+	// If the returned error is a wrapper error, implementations should make sure that
+	// the error implements Temporary() to have the correct retry behaviors.
 	ClientHandshake(context.Context, string, net.Conn) (net.Conn, AuthInfo, error)
 	// ServerHandshake does the authentication handshake for servers. It returns
 	// the authenticated connection and the corresponding auth information about
@@ -192,14 +181,14 @@ func NewTLS(c *tls.Config) TransportCredentials {
 	return tc
 }
 
-// NewClientTLSFromCert constructs a TLS from the input certificate for client.
+// NewClientTLSFromCert constructs TLS credentials from the input certificate for client.
 // serverNameOverride is for testing only. If set to a non empty string,
 // it will override the virtual host name of authority (e.g. :authority header field) in requests.
 func NewClientTLSFromCert(cp *x509.CertPool, serverNameOverride string) TransportCredentials {
 	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp})
 }
 
-// NewClientTLSFromFile constructs a TLS from the input certificate file for client.
+// NewClientTLSFromFile constructs TLS credentials from the input certificate file for client.
 // serverNameOverride is for testing only. If set to a non empty string,
 // it will override the virtual host name of authority (e.g. :authority header field) in requests.
 func NewClientTLSFromFile(certFile, serverNameOverride string) (TransportCredentials, error) {
@@ -214,12 +203,12 @@ func NewClientTLSFromFile(certFile, serverNameOverride string) (TransportCredent
 	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp}), nil
 }
 
-// NewServerTLSFromCert constructs a TLS from the input certificate for server.
+// NewServerTLSFromCert constructs TLS credentials from the input certificate for server.
 func NewServerTLSFromCert(cert *tls.Certificate) TransportCredentials {
 	return NewTLS(&tls.Config{Certificates: []tls.Certificate{*cert}})
 }
 
-// NewServerTLSFromFile constructs a TLS from the input certificate file and key
+// NewServerTLSFromFile constructs TLS credentials from the input certificate file and key
 // file for server.
 func NewServerTLSFromFile(certFile, keyFile string) (TransportCredentials, error) {
 	cert, err := tls.LoadX509KeyPair(certFile, keyFile)