Updates vendored Raft library.

This pulls in https://github.com/hashicorp/raft/pull/207 to get
support for the new-style peers.json recovery file.

vendor/github.com/hashicorp/raft/peersjson.go

@@ -44,3 +44,55 @@ func ReadPeersJSON(path string) (Configuration, error) {
 	}
 	return configuration, nil
 }
+
+// configEntry is used when decoding a new-style peers.json.
+type configEntry struct {
+	// ID is the ID of the server (a UUID, usually).
+	ID ServerID `json:"id"`
+
+	// Address is the host:port of the server.
+	Address ServerAddress `json:"address"`
+
+	// NonVoter controls the suffrage. We choose this sense so people
+	// can leave this out and get a Voter by default.
+	NonVoter bool `json:"non_voter"`
+}
+
+// ReadConfigJSON reads a new-style peers.json and returns a configuration
+// structure. This can be used to perform manual recovery when running protocol
+// versions that use server IDs.
+func ReadConfigJSON(path string) (Configuration, error) {
+	// Read in the file.
+	buf, err := ioutil.ReadFile(path)
+	if err != nil {
+		return Configuration{}, err
+	}
+
+	// Parse it as JSON.
+	var peers []configEntry
+	dec := json.NewDecoder(bytes.NewReader(buf))
+	if err := dec.Decode(&peers); err != nil {
+		return Configuration{}, err
+	}
+
+	// Map it into the new-style configuration structure.
+	var configuration Configuration
+	for _, peer := range peers {
+		suffrage := Voter
+		if peer.NonVoter {
+			suffrage = Nonvoter
+		}
+		server := Server{
+			Suffrage: suffrage,
+			ID:       peer.ID,
+			Address:  peer.Address,
+		}
+		configuration.Servers = append(configuration.Servers, server)
+	}
+
+	// We should only ingest valid configurations.
+	if err := checkConfiguration(configuration); err != nil {
+		return Configuration{}, err
+	}
+	return configuration, nil
+}

vendor/vendor.json

@@ -612,10 +612,10 @@
 			"revisionTime": "2015-11-16T02:03:38Z"
 		},
 		{
-			"checksumSHA1": "NvFexY/rs9sPfve+ny/rkMkCL5M=",
+			"checksumSHA1": "8Na6qG9taUXHDunMYecGxbHbJKE=",
 			"path": "github.com/hashicorp/raft",
-			"revision": "6b063a18bfe6e0da3fdc2b9bf6256be9c0a4849a",
+			"revision": "939ebd2103731c2f38c7964d8dd24af0e1b26dc3",
-			"revisionTime": "2017-03-16T02:42:32Z",
+			"revisionTime": "2017-05-04T20:16:11Z",
 			"version": "library-v2-stage-one",
 			"versionExact": "library-v2-stage-one"
 		},