cryptocore: remove lastNonce check

This check would need locking to be multithreading-safe.
But as it is in the fastpath, just remove it.
rand.Read() already guarantees that the value is random.

internal/cryptocore/nonce.go

@@ -1,14 +1,9 @@
 package cryptocore
 
 import (
-	"bytes"
 	"crypto/rand"
 	"encoding/binary"
-	"encoding/hex"
-	"fmt"
 	"log"
-
-	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
 // RandBytes gets "n" random bytes from /dev/urandom or panics
@@ -28,18 +23,11 @@ func RandUint64() uint64 {
 }
 
 type nonceGenerator struct {
-	lastNonce []byte
-	nonceLen  int // bytes
+	nonceLen int // bytes
 }
 
 // Get a random "nonceLen"-byte nonce
 func (n *nonceGenerator) Get() []byte {
 	nonce := RandBytes(n.nonceLen)
-	tlog.Debug.Printf("nonceGenerator.Get(): %s\n", hex.EncodeToString(nonce))
-	if bytes.Equal(nonce, n.lastNonce) {
-		m := fmt.Sprintf("Got the same nonce twice: %s. This should never happen!", hex.EncodeToString(nonce))
-		log.Panic(m)
-	}
-	n.lastNonce = nonce
 	return nonce
 }