[SPARK-20439][SQL] Fix Catalog API listTables and getTable when failed to fetch table metadata

### What changes were proposed in this pull request?

`spark.catalog.listTables` and `spark.catalog.getTable` does not work if we are unable to retrieve table metadata due to any reason (e.g., table serde class is not accessible or the table type is not accepted by Spark SQL). After this PR, the APIs still return the corresponding Table without the description and tableType)

### How was this patch tested?
Added a test case

Author: Xiao Li <gatorsmile@gmail.com>

Closes #17730 from gatorsmile/listTables.