Cherry-pick #9069 to 6.5: Propagate Sync error when running SafeFileR…

…otate (#9142)

* Propagate Sync error when running SafeFileRotate (#9069)

Previously, it was possible SafeFileRotate encountered an error without propagating it, because the return value of os.Sync was not utilized.
From now on the errors from Sync are propagated.
(cherry picked from commit 93eb92a)

CHANGELOG.asciidoc

@@ -33,6 +33,8 @@ https://github.com/elastic/beats/compare/v6.5.1...6.5[Check the HEAD diff]
 
 *Affecting all Beats*
 
+- Propagate Sync error when running SafeFileRotate. {pull}9069[9069]
+
 *Auditbeat*
 
 *Filebeat*

libbeat/common/file/helper_other.go

@@ -40,7 +40,6 @@ func SafeFileRotate(path, tempfile string) error {
 		return nil // ignore error
 	}
 	defer f.Close()
-	f.Sync()
 
-	return nil
+	return f.Sync()
 }