Add HashiCorp Nomad provider (#483)

* provider: adding Nomad provider

* updating CONTRIBUTING.md with Nomad provider

* updated README.md by adding the Nomad provider

* fix typo

* adding nomad/api and nomad/testutil deps

* adding Nomad binary dependency for provider tests

* fixed the nomad binary download command step and added tolerations to the nomad provider.

* adding nomad provider demo gif

* adding my name to authors

* adding two missing go-rootcerts files after dep ensure

* delete pod comment

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

@@ -0,0 +1,133 @@
+package raft
+
+import (
+	"bytes"
+	crand "crypto/rand"
+	"fmt"
+	"math"
+	"math/big"
+	"math/rand"
+	"time"
+
+	"github.com/hashicorp/go-msgpack/codec"
+)
+
+func init() {
+	// Ensure we use a high-entropy seed for the psuedo-random generator
+	rand.Seed(newSeed())
+}
+
+// returns an int64 from a crypto random source
+// can be used to seed a source for a math/rand.
+func newSeed() int64 {
+	r, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
+	if err != nil {
+		panic(fmt.Errorf("failed to read random bytes: %v", err))
+	}
+	return r.Int64()
+}
+
+// randomTimeout returns a value that is between the minVal and 2x minVal.
+func randomTimeout(minVal time.Duration) <-chan time.Time {
+	if minVal == 0 {
+		return nil
+	}
+	extra := (time.Duration(rand.Int63()) % minVal)
+	return time.After(minVal + extra)
+}
+
+// min returns the minimum.
+func min(a, b uint64) uint64 {
+	if a <= b {
+		return a
+	}
+	return b
+}
+
+// max returns the maximum.
+func max(a, b uint64) uint64 {
+	if a >= b {
+		return a
+	}
+	return b
+}
+
+// generateUUID is used to generate a random UUID.
+func generateUUID() string {
+	buf := make([]byte, 16)
+	if _, err := crand.Read(buf); err != nil {
+		panic(fmt.Errorf("failed to read random bytes: %v", err))
+	}
+
+	return fmt.Sprintf("%08x-%04x-%04x-%04x-%12x",
+		buf[0:4],
+		buf[4:6],
+		buf[6:8],
+		buf[8:10],
+		buf[10:16])
+}
+
+// asyncNotifyCh is used to do an async channel send
+// to a single channel without blocking.
+func asyncNotifyCh(ch chan struct{}) {
+	select {
+	case ch <- struct{}{}:
+	default:
+	}
+}
+
+// drainNotifyCh empties out a single-item notification channel without
+// blocking, and returns whether it received anything.
+func drainNotifyCh(ch chan struct{}) bool {
+	select {
+	case <-ch:
+		return true
+	default:
+		return false
+	}
+}
+
+// asyncNotifyBool is used to do an async notification
+// on a bool channel.
+func asyncNotifyBool(ch chan bool, v bool) {
+	select {
+	case ch <- v:
+	default:
+	}
+}
+
+// Decode reverses the encode operation on a byte slice input.
+func decodeMsgPack(buf []byte, out interface{}) error {
+	r := bytes.NewBuffer(buf)
+	hd := codec.MsgpackHandle{}
+	dec := codec.NewDecoder(r, &hd)
+	return dec.Decode(out)
+}
+
+// Encode writes an encoded object to a new bytes buffer.
+func encodeMsgPack(in interface{}) (*bytes.Buffer, error) {
+	buf := bytes.NewBuffer(nil)
+	hd := codec.MsgpackHandle{}
+	enc := codec.NewEncoder(buf, &hd)
+	err := enc.Encode(in)
+	return buf, err
+}
+
+// backoff is used to compute an exponential backoff
+// duration. Base time is scaled by the current round,
+// up to some maximum scale factor.
+func backoff(base time.Duration, round, limit uint64) time.Duration {
+	power := min(round, limit)
+	for power > 2 {
+		base *= 2
+		power--
+	}
+	return base
+}
+
+// Needed for sorting []uint64, used to determine commitment
+type uint64Slice []uint64
+
+func (p uint64Slice) Len() int           { return len(p) }
+func (p uint64Slice) Less(i, j int) bool { return p[i] < p[j] }
+func (p uint64Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }