R1:cea58de0ba92

Fixed naming convention violations.

Summary: This file contains member variables prefixed with underscores. This violates the naming convention enforced by the linter.

Test Plan:
The linter warnings have disappeared. Example:
```
>>> Lint for src/infrastructure/storage/lisk/LiskDAO.php:

Warning (XHP9) Naming Conventions
Follow naming conventions: class properties should be named using
lowerCamelCase.

183
184 const COUNTER_TABLE_NAME = 'lisk_counter'…