lib/kadm5: kadm_connect do not close 's' more than once

If 's' is closed before exiting, it must be set to rk_INVALID_SOCKET.

Change-Id: I63caf992aa3a6b2c86c918a660025fc054d396d6

lib/kadm5/init_c.c

@@ -530,6 +530,7 @@ kadm_connect(kadm5_client_context *ctx)
 	if (connect(s, a->ai_addr, a->ai_addrlen) < 0) {
 	    krb5_warn(context, errno, "connect(%s)", hostname);
 	    rk_closesocket(s);
+	    s = rk_INVALID_SOCKET;
 	    continue;
 	}
 	break;