**Apache Airflow version**: 1.10.12

**Environment**:  Centos 7 Host

- **Cloud provider or hardware configuration**: 
- **OS** (e.g. from /etc/os-release): Ubuntu 20.04 Docker Container
- **Kernel** (e.g. `uname -a`): Linux c6c6e8230c17 3.10.0-1127.18.2.el7.x86_64 #1 SMP Sun Jul 26 15:27:06 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
- **Install tools**: Docker Compose
- **Others** ?

**What happened**:

The schema file generated by MSSQLToGCSOperator specifies that a field defined as **bit** in MSSQL, is defined as **INTEGER**.  However, the JSON file defines the value as **true**/**false**.  When attempting to import into BigQuery using the GCSOperatorToBigQuery operator, the job fails:
`Error while reading data, error message: JSON parsing error in row starting at position 0: Could not convert value 'boolean_value: false' to integer. Field: manager; Value: 0`

**What you expected to happen**:

Value should be defined as **BOOLEAN** in the schema.

**How to reproduce it**:
Ensure `dbo.Customers` table has a **bit** column:

```
export_customers = MsSqlToGoogleCloudStorageOperator(
                task_id='export_customers',
                sql='SELECT * FROM dbo.Customers;',
                bucket='mssql-export',
                filename='data/customers/export.json',
                schema_filename='schemas/export.json',
                mssql_conn_id='mssql_default',
                google_cloud_storage_conn_id='google_cloud_default',
                dag=dag
            )
```
CURSOR_DESCRIPTION = (
    ("some_str", 0, None, None, None, None, None),
    ("some_num", 3, None, None, None, None, None),
)
NDJSON_LINES = [
    b'{"some_num": 42, "some_str": "mock_row_content_1"}\n',
    b'{"some_num": 43, "some_str": "mock_row_content_2"}\n',
    b'{"some_num": 44, "some_str": "mock_row_content_3"}\n',
]
SCHEMA_FILENAME = "schema_test.json"
SCHEMA_JSON = [
    b'[{"mode": "NULLABLE", "name": "some_str", "type": "STRING"}, ',
    b'{"mode": "NULLABLE", "name": "some_num", "type": "INTEGER"}]',
]
@pytest.mark.backend("mssql")
class TestMsSqlToGoogleCloudStorageOperator:
    @pytest.mark.parametrize(
        "value, expected",
        [
            ("string", "string"),
            (32.9, 32.9),
            (-2, -2),
            (datetime.date(1970, 1, 2), "1970-01-02"),
            (datetime.date(1000, 1, 2), "1000-01-02"),
            (datetime.datetime(1970, 1, 1, 1, 0), "1970-01-01T01:00:00"),
            (datetime.time(hour=0, minute=0, second=0), "00:00:00"),
            (datetime.time(hour=23, minute=59, second=59), "23:59:59"),
        ],
    )
    def test_convert_type(self, value, expected):