[udisks] Don't add/remove devices in slotMediaChanged
We get notified when devices are added via InterfacesAdded/InterfacesRemoved.
When ejecting from a CD drive we first get slotMediaChanged, where we remove the device from m_deviceCache. Then we get InterfacesRemoved for org.freedesktop.UDisks2.Filesystem. Because the org.freedesktop.UDisks2.Block interface is still there we remove and immediately readd the device. Then in DeviceManagerPrivate::_k_deviceAdded we call createBackendObject, which fails to create a backend because the uid is not in m_deviceCache any more. Then we assert because the backend is empty.
SENTRY: KIO-6S
SENTRY: KONTACT-FM
SENTRY: KDED-P
SENTRY: PLASMA-WORKSPACE-SMH
SENTRY: ARK-5T
SENTRY: DOLPHIN-218