Correctly unmarshal Protocol (elastic#17843)

The Protocol (https/http) was not correctly unmarshaly and assigned to
the value of the struct. Because of this the checking was trying to use
a plain text connection or a TLS enabled endpoint.

Fixes: elastic#17841
(cherry picked from commit 0765f94)

x-pack/elastic-agent/CHANGELOG.asciidoc

@@ -21,6 +21,7 @@
 - Fix issues when running `mage package` for all the platforms. {pull}17767[17767]
 - Rename the User-Agent string from Beats Agent to Elastic Agent. {pull}17765[17765]
 - Remove the kbn-version on each request to the Kibana API. {pull}17764[17764]
+- Make sure that the Elastic Agent connect over TLS in cloud. {pull}17843[17843]
 
 ==== New features
 

x-pack/elastic-agent/pkg/kibana/config.go

@@ -31,6 +31,8 @@ func (p *Protocol) Unpack(from string) error {
 	if from != "https" && from != "http" {
 		return fmt.Errorf("invalid protocol %s, accepted values are 'http' and 'https'", from)
 	}
+
+	*p = Protocol(from)
 	return nil
 }
 

x-pack/elastic-agent/pkg/kibana/config_test.go

@@ -0,0 +1,37 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package kibana
+
+import (
+	"reflect"
+	"testing"
+	"time"
+
+	"gopkg.in/yaml.v2"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPackUnpack(t *testing.T) {
+	c := Config{
+		Protocol: Protocol("https"),
+		SpaceID:  "123",
+		Username: "foo",
+		Password: "bar",
+		Path:     "/ok",
+		Timeout:  10 * time.Second,
+	}
+
+	b, err := yaml.Marshal(&c)
+	require.NoError(t, err)
+
+	c2 := Config{}
+
+	err = yaml.Unmarshal(b, &c2)
+	require.NoError(t, err)
+
+	assert.True(t, reflect.DeepEqual(c, c2))
+}