network: handle interface renaming property

With this patch, we connect to the device interface property to update the valid persistent connections list per device when interface renaming happens. A typical use case is when android USB tethering is enabled. The _deviceAdded() method is invoked with ifname usb0 some milliseconds before the interface is renamed to something like enp0s20f0u1 depending on the port the phone is plugged on. gnome-shell in this case will ignore the new interface name. If the user has customized a previous USB Ethernet connection with a fixed interface name, this connection won't be associated to this device, and a new temporary connection will be created instead. Another user visible difference is that such tethering connection now appears correctly as "USB Ethernet" instead of "Ethernet" in the panel, due to the NetworkManager disambiguation update triggered by this interface renaming.