Add the creator of the board as a administrator of the board if it still belongs to the channel (#3454)

server/services/store/sqlstore/migrations/000018_add_teams_and_boards.up.sql

@@ -302,7 +302,7 @@ INSERT INTO {{.prefix}}board_members (
     SELECT B.Id, CM.UserId, CM.Roles, TRUE, TRUE, FALSE, FALSE
     FROM {{.prefix}}boards AS B
     INNER JOIN ChannelMembers as CM ON CM.ChannelId=B.channel_id
-    WHERE CM.SchemeAdmin=True
+    WHERE CM.SchemeAdmin=True OR (CM.UserId=B.created_by)
 );
 {{end}}