Update go-plugin

vendor/github.com/hashicorp/go-plugin/testing.go

@@ -3,6 +3,7 @@ package plugin
 import (
 	"bytes"
 	"context"
+	"io"
 	"net"
 	"net/rpc"
 
@@ -10,6 +11,18 @@ import (
 	"google.golang.org/grpc"
 )
 
+// TestOptions allows specifying options that can affect the behavior of the
+// test functions
+type TestOptions struct {
+	//ServerStdout causes the given value to be used in place of a blank buffer
+	//for RPCServer's Stdout
+	ServerStdout io.ReadCloser
+
+	//ServerStderr causes the given value to be used in place of a blank buffer
+	//for RPCServer's Stderr
+	ServerStderr io.ReadCloser
+}
+
 // The testing file contains test helpers that you can use outside of
 // this package for making it easier to test plugins themselves.
 
@@ -61,12 +74,20 @@ func TestRPCConn(t testing.T) (*rpc.Client, *rpc.Server) {
 
 // TestPluginRPCConn returns a plugin RPC client and server that are connected
 // together and configured.
-func TestPluginRPCConn(t testing.T, ps map[string]Plugin) (*RPCClient, *RPCServer) {
+func TestPluginRPCConn(t testing.T, ps map[string]Plugin, opts *TestOptions) (*RPCClient, *RPCServer) {
 	// Create two net.Conns we can use to shuttle our control connection
 	clientConn, serverConn := TestConn(t)
 
 	// Start up the server
 	server := &RPCServer{Plugins: ps, Stdout: new(bytes.Buffer), Stderr: new(bytes.Buffer)}
+	if opts != nil {
+		if opts.ServerStdout != nil {
+			server.Stdout = opts.ServerStdout
+		}
+		if opts.ServerStderr != nil {
+			server.Stderr = opts.ServerStderr
+		}
+	}
 	go server.ServeConn(serverConn)
 
 	// Connect the client to the server

vendor/vendor.json

@@ -1003,10 +1003,10 @@
 			"revisionTime": "2017-12-04T18:29:08Z"
 		},
 		{
-			"checksumSHA1": "y3op+t01flBlSBKlzUNqH5d4XHQ=",
+			"checksumSHA1": "7SheX5w6+xGsTMxPI3LiJx0iz7s=",
 			"path": "github.com/hashicorp/go-plugin",
-			"revision": "e53f54cbf51efde642d4711313e829a1ff0c236d",
-			"revisionTime": "2018-01-25T19:04:38Z"
+			"revision": "4b17561773d85e482ea040884ee3e288425d4174",
+			"revisionTime": "2018-02-06T18:30:35Z"
 		},
 		{
 			"checksumSHA1": "yzoWV7yrS/TvOrKy5ZrdUjsYaOA=",