rpc: Check and message setsockopt()

Check status when attempting to set SO_REUSEADDR flag on outgoing connection
On failure, VIR_WARN(), but continue to connect. This code path is on the
sender side where the setting is just a hint and would only take effect if
the sender is overflowed with TCP connections.  Inability to set doesn't mean
failure to establish a connection.

src/rpc/virnetsocket.c

@@ -473,7 +473,9 @@ int virNetSocketNewConnectTCP(const char *nodename,
             goto error;
         }
 
-        setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
+        if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {
+            VIR_WARN("Unable to enable port reuse");
+        }
 
         if (connect(fd, runp->ai_addr, runp->ai_addrlen) >= 0)
             break;