RADIUS client: Do not try to send message without socket

[Tristan]

Commit 9ed4076673 breaks radius if hostapd comes up before routes to the
auth/acct servers are in place.

That is, if the routing daemon gets the route to auth server over a
wireless interface that it started at the same time as the one hostapd
serves, hostapd usually fails the connect on the udp sockets for the auth
and acct servers, and this patch disables the pathway to reopen the
connection.

Cheers,
Tristan

-- 
All original matter is hereby placed immediately under the public domain.