add gocritic/ruleguard checks back again, cleanup code. (#13665)

- remove some duplicated code
- reported a bug, separately fixed in #13664
- using strings.ReplaceAll() when needed
- using filepath.ToSlash() use when needed
- remove all non-Go style comments from the codebase

Co-authored-by: Aditya Manthramurthy <donatello@users.noreply.github.com>

internal/event/target/mqtt.go

@@ -272,10 +272,8 @@ func NewMQTTTarget(id string, args MQTTArgs, doneCh <-chan struct{}, loggerOnce
 			// Start replaying events from the store.
 			go sendEvents(target, eventKeyCh, doneCh, target.loggerOnce)
 		}
-	} else {
-		if token.Wait() && token.Error() != nil {
-			return target, token.Error()
-		}
+	} else if token.Wait() && token.Error() != nil {
+		return target, token.Error()
 	}
 	return target, nil
 }