[Hive Metastore] Add a Configuration Item to Skip the HDFS Data Modification

["Chang.Wu" <58...@qq.com>]

As stated in HIVE-20398

When we are conducting the hive upgrading,  we have following use case:

We want to sync the operations between two metastore server (A and B) by thrift api, but both them are based on the same HDFS. So, for operations like drop_partitions, drop_table,  insert_overwrite, create_table which will cause the data modification in HDFS, we want it to be executed by only Metastore Server A. For metastore Server B, he will only change his metadata, but didn't do corresponding HDFS files operation.

So, we need a switch to control this.

like 

 
hive.metastore.skip.hdfs
whose default value is false just like what is happening now.

When its value is true, the metastore server will only conduct the metadata modification, but skip the HDFS data modification.