Major Description
Spark 2.x implements create table by itself.
https://github.com/apache/spark/commit/7d2ed8cc030f3d84fea47fded072c320c3d87ca7
But in the implement mentioned above, it remove table comment from properties, so user can not see table comment through run "describe formatted table". Similarly, when user alters table comment, he still can not see the change of table comment through run "describe formatted table".
I wonder why we removed table comments, is this a bug?
