Rename mbedtls_net_close() to mbedtls_net_free()

close() may be more meaningful, but free() is symmetric with _init(), and more
consistent with all other modules
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 27bd8bf..773bca6 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -1503,7 +1503,7 @@
     {
         --opt.reconnect;
 
-        mbedtls_net_close( &server_fd );
+        mbedtls_net_free( &server_fd );
 
 #if defined(MBEDTLS_TIMING_C)
         if( opt.reco_delay > 0 )
@@ -1572,7 +1572,7 @@
     }
 #endif
 
-    mbedtls_net_close( &server_fd );
+    mbedtls_net_free( &server_fd );
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
     mbedtls_x509_crt_free( &clicert );