Disable monitoring during fleetserver bootstrap process (#27222)

* Disable monitoring during fleetserver bootstrap process

Set the monitoring.enabled flag to false during the fleet-server
bootstrap process in order to ensure that no data is sent to an
elasticsearch instance running on the same host.

* Add CHANGELOG entry

x-pack/elastic-agent/CHANGELOG.next.asciidoc

@@ -77,6 +77,7 @@
 - Remove symlink.prev from previously failed upgrade {pull}26785[26785]
 - Fix apm-server supported outputs not being in sync with supported output types. {pull}26885[26885]
 - Set permissions during installation {pull}26665[26665]
+- Disable monitoring during fleet-server bootstrapping. {pull}27222[27222]
 
 ==== New features
 

x-pack/elastic-agent/pkg/agent/application/fleet_server_bootstrap.go

@@ -24,6 +24,7 @@ import (
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/config"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/logger"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/monitoring"
+	monitoringCfg "github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/monitoring/config"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/server"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/status"
 	reporting "github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/reporter"
@@ -85,6 +86,11 @@ func newFleetServerBootstrap(
 
 	reporter := reporting.NewReporter(bootstrapApp.bgContext, log, bootstrapApp.agentInfo, logR)
 
+	if cfg.Settings.MonitoringConfig != nil {
+		cfg.Settings.MonitoringConfig.Enabled = false
+	} else {
+		cfg.Settings.MonitoringConfig = &monitoringCfg.MonitoringConfig{Enabled: false}
+	}
 	monitor, err := monitoring.NewMonitor(cfg.Settings)
 	if err != nil {
 		return nil, errors.New(err, "failed to initialize monitoring")