RADIUS client: Fix server connection recovery after initial failure

RADIUS client: Fix server connection recovery after initial failure

If the initial attempt at opening the socket connection to the RADIUS
server failed due to missing IP connectivity during startup, e.g., with
"connect[radius]: Network is unreachable", hostapd did not try to
reconnect when RADIUS messages were sent. Instead, it only reported "No
authentication server configured" even if the configuration did have a
server entry.

This was broken by commit 9ed40766735a9628cc6c936076b175e6f66534bb
('RADIUS client: Do not try to send message without socket') for the
initial case and the more recent fixes in RADIUS server failover cases
did not cover the initial failure case.

Signed-off-by: Jouni Malinen <j@w1.fi>