Actually use the READ_TIMEOUT_MS in the sample DTLS client and server

Signed-off-by: Ryan LaPointe <ryan@ryanlapointe.org>
diff --git a/programs/ssl/dtls_server.c b/programs/ssl/dtls_server.c
index 22e3fc5..958b0b5 100644
--- a/programs/ssl/dtls_server.c
+++ b/programs/ssl/dtls_server.c
@@ -223,6 +223,7 @@
 
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
+    mbedtls_ssl_conf_read_timeout( &conf, READ_TIMEOUT_MS );
 
 #if defined(MBEDTLS_SSL_CACHE_C)
     mbedtls_ssl_conf_session_cache( &conf, &cache,