[Elastic Agent] Fix the platform reporting and the family reporting. (#…

…18666) (#18731)

* [Elastic Agent] Fix the platform reporting and the family reporting.

This PR fixes:

- Report Family correctly: redhat/debian.
- Report the platform correctly Centos for Centos instead of redhat.

Fixes: #18665
(cherry picked from commit 235df7b)

x-pack/elastic-agent/CHANGELOG.asciidoc

@@ -40,6 +40,7 @@
 - Remove fleet admin from setup script {pull}18611[18611]
 - Clean action store after enrolling to new configuration {pull}18656[18656]
 - Avoid watching monitor logs {pull}18723[18723]
+- Correctly report platform and family. {issue}18665[18665]
 
 ==== New features
 

x-pack/elastic-agent/pkg/agent/application/info/agent_metadata.go

@@ -141,9 +141,9 @@ func (i *AgentInfo) ECSMetadata() (*ECSMeta, error) {
 
 		// Operating system
 		OS: &SystemECSMeta{
-			Family:   runtime.GOOS,
+			Family:   info.OS.Family,
 			Kernel:   info.KernelVersion,
-			Platform: info.OS.Family,
+			Platform: info.OS.Platform,
 			Version:  info.OS.Version,
 			Name:     info.OS.Name,
 			FullName: getFullOSName(info),