expect_column_values_to_not_be_null duplicates columns in unexpected values query

[kujaska]

Describe the bug
expect_column_values_to_not_be_null duplicates columns in unexpected values query:

To Reproduce
if you have defined checkpoint like this:
a) query as
Select col1, col2, col3
FROM table1

b) runtime_configuration

runtime_configuration: {
"result_format": {
"result_format": "COMPLETE",
"unexpected_index_column_names": ["col1",
"col2",
"col3"
],
"return_unexpected_index_query": True,
"partial_unexpected_count": 20
}
}

and expectation expect_column_values_to_not_be_null for col1

then you will get this SQL in checkpoint result JSON and DataDocs:

To retrieve all unexpected values...
SELECT col1, col2, col3, col1
FROM [#gx_temp_123]
WHERE col1 IS NULL;

• notice 2nd occurrence of col1

Expected behavior
unexpected values query does not duplicate columns:

SELECT col1, col2, col3
FROM [#gx_temp_123]
WHERE col1 IS NULL;

Environment (please complete the following information):

• Operating System: Linux (Ubuntu)
• Great Expectations Version: 0.18.1
• Data Source: MS SQL
• Cloud environment: Local virtual machine