[dataengines/powermanagement] Factor out setting data.Battery.Sources

In other places both properties are being set unconditionally, so this
patch just aligns it to other code. Also, possibly fixing scenario
where the Sources property might de-synchronize because the code
conditionally skipped updating it.

dataengines/powermanagement/powermanagementengine.cpp

@@ -237,9 +237,9 @@ bool PowermanagementEngine::sourceRequestEvent(const QString &name)
         updateBatteryNames();
         updateOverallBattery();
 
+        setData(QStringLiteral("Battery"), QStringLiteral("Sources"), batterySources);
         setData(QStringLiteral("Battery"), QStringLiteral("Has Battery"), !batterySources.isEmpty());
         if (!batterySources.isEmpty()) {
-            setData(QStringLiteral("Battery"), QStringLiteral("Sources"), batterySources);
             QDBusMessage msg = QDBusMessage::createMethodCall(SOLID_POWERMANAGEMENT_SERVICE,
                                                               QStringLiteral("/org/kde/Solid/PowerManagement"),
                                                               SOLID_POWERMANAGEMENT_SERVICE,