talksapp: do not return an error if memcache is down

Memcache outages should not cause down time.

Change-Id: If63a90904cae3d70189e7026775f3019bbda4768
Reviewed-on: https://go-review.googlesource.com/29811
Reviewed-by: Jaana Burcu Dogan <jbd@google.com>
diff --git a/talksapp/main.go b/talksapp/main.go
index 5810518..c03ddab 100644
--- a/talksapp/main.go
+++ b/talksapp/main.go
@@ -189,7 +189,7 @@
 		w.Write(item.Value)
 		return nil
 	} else if err != memcache.ErrCacheMiss {
-		return err
+		log.Errorf(ctx, "Could not get item from Memcache: %v", err)
 	}
 
 	log.Infof(ctx, "Fetching presentation %s.", importPath)