validate row: Impala pads decimals causing validation failures

Note the output below:
```
select cast(col_dec_10_2 as string) from pso_data_validator.dvt_core_types;

+------------------------------+
| cast(col_dec_10_2 as string) |
+------------------------------+
| 123.11 |
| 123.22 |
| 123.30 |
+------------------------------+
```

Other supported engines would not pad `123.3` with a trailing zero.

Search for "issue-1379" in test_impala.py when resolving this issue.