enc: save entropy probs only when needed for refresh

Previous entropy probs need to be saved (and restored) only when
current updates are not propagated.

Change-Id: Ie6ee0543066e30874e56258be0a6b7d2dd2fdb2b

vp8/encoder/bitstream.c

diff --git a/vp8/encoder/bitstream.c b/vp8/encoder/bitstream.c
index cea8e12..a4d05fb 100644
--- a/vp8/encoder/bitstream.c
+++ b/vp8/encoder/bitstream.c
@@ -1784,9 +1784,9 @@
 
     vp8_clear_system_state();  //__asm emms;
 
-    //************************************************
-    // save a copy for later refresh
+    if (pc->refresh_entropy_probs == 0)
     {
+        // save a copy for later refresh
         vpx_memcpy(&cpi->common.lfc, &cpi->common.fc, sizeof(cpi->common.fc));
     }