sd-network: expose both admin and operational state directly

Also add a call to check if a link is loopback, as this should commonly be ignored.

src/libsystemd-network/network-internal.h

@@ -65,5 +65,3 @@ int config_parse_ifalias(const char *unit, const char *filename, unsigned line,
 int net_parse_inaddr(const char *address, unsigned char *family, void *dst);
 
 int net_get_unique_predictable_data(struct udev_device *device, uint8_t result[8]);
-
-bool link_has_carrier(unsigned flags, uint8_t operstate);