Fail to get table constrains of Hive tables with Spark API

Now we can not get table constrains like `not null` with Spark API. It may be the bug of Spark.

Here is the process to re-produce the issue.

We can create the table with constrains with hive.

```
create table notnull_col_table2 (col1 int not null, col2 int);
```

But we may not get the not null constrains with Spark API.

```
def main(argv: Array[String]): Unit = {

val spark = SparkSession.builder()
.master("local")
.config("spark.hadoop.hive.metastore.uris", "thrift://localhost:9083")
.config("spark.sql.catalogImplementation", "hive")
.getOrCreate()

val df = spark.table("db1.notnull_col_table2")

val schema = df.schema
println(schema) # StructType(StructField(col1,IntegerType,true),StructField(col2,IntegerType,true))

val col1_schema = schema.fields(0)
println(col1_schema.nullable) # true
}
```