update live tv images

MediaBrowser.Controller/Entities/BaseItem.cs

@@ -1536,6 +1536,7 @@ namespace MediaBrowser.Controller.Entities
 
                 image.Path = file.FullName;
                 image.DateModified = imageInfo.DateModified;
+                image.IsPlaceholder = false;
             }
         }
 

MediaBrowser.Controller/Entities/ItemImageInfo.cs

@@ -24,6 +24,12 @@ namespace MediaBrowser.Controller.Entities
         /// <value>The date modified.</value>
         public DateTime DateModified { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether this instance is placeholder.
+        /// </summary>
+        /// <value><c>true</c> if this instance is placeholder; otherwise, <c>false</c>.</value>
+        public bool IsPlaceholder { get; set; }
+        
         [IgnoreDataMember]
         public bool IsLocalFile
         {