server/vault: tweak error messages

Closes #5139

nomad/vault.go

@@ -438,7 +438,7 @@ OUTER:
 				retryTimer.Reset(v.config.ConnectionRetryIntv)
 				v.l.Lock()
 				v.connEstablished = true
-				v.connEstablishedErr = fmt.Errorf("Nomad Server failed to establish connections to Vault: %v", err)
+				v.connEstablishedErr = fmt.Errorf("failed to establish connection to Vault: %v", err)
 				v.l.Unlock()
 				continue OUTER
 			}
@@ -517,7 +517,8 @@ func (v *vaultClient) renewalLoop() {
 			if backoff < 0 {
 				// We have failed to renew the token past its expiration. Stop
 				// renewing with Vault.
-				v.logger.Error("failed to renew Vault token before lease expiration. Shutting down Vault client")
+				v.logger.Error("failed to renew Vault token before lease expiration. Shutting down Vault client",
+					"error", err)
 				v.l.Lock()
 				v.connEstablished = false
 				v.connEstablishedErr = err

nomad/vault_test.go

@@ -1119,7 +1119,7 @@ func TestVaultClient_CreateToken_Role_InvalidToken(t *testing.T) {
 	task.Vault = &structs.Vault{Policies: []string{"default"}}
 
 	_, err = client.CreateToken(context.Background(), a, task.Name)
-	if err == nil || !strings.Contains(err.Error(), "Nomad Server failed to establish connections to Vault") {
+	if err == nil || !strings.Contains(err.Error(), "failed to establish connection to Vault") {
 		t.Fatalf("CreateToken should have failed: %v", err)
 	}
 }