Ease the write permissions on external table during create table operation

During the creation of external tables with a specified location, the general expectation is that the data is already present or the data might be externally added to the location without involving HMS. So, it is really not required to have read and write permissions on an external table during the creation time.

This enhancement can address security concerns where currently the users had to be granted unnecessary write permissions on an external file location when the table is only used for reading the data.

Update/delete operations would anyway require write permissions.

CTAS query with location specified is expected to fail at runtime (trying to create staging directory under table location) without WRITE permissions.