[seg] Initialize temporal_update flag

Initialization has been nowhere done for seg->temporal_update.

Change-Id: I3ccc0e10e14a83859b683c026093b921ea6d5dbf
diff --git a/av1/encoder/segmentation.c b/av1/encoder/segmentation.c
index 6ed9933..b649a77 100644
--- a/av1/encoder/segmentation.c
+++ b/av1/encoder/segmentation.c
@@ -23,12 +23,14 @@
   seg->enabled = 1;
   seg->update_map = 1;
   seg->update_data = 1;
+  seg->temporal_update = 0;
 }
 
 void av1_disable_segmentation(struct segmentation *seg) {
   seg->enabled = 0;
   seg->update_map = 0;
   seg->update_data = 0;
+  seg->temporal_update = 0;
 }
 
 void av1_disable_segfeature(struct segmentation *seg, int segment_id,