Found by Ricardo Salveti de Araujo <ricardo.salveti@openbossa.org>

The link cache was updated immediately, but the carrier state signals
were emitted a lot later, when the cache data was already stale.  So
just update the cache at the same time we emit the signals.  The
carrier-state-request stuff wasn't originally converted to deferred
for any netlink-specific reason, just to smooth the initial device
creation process in NM.