Fix incorrect baker data in accounts

[vishakh]

Problem: The Tezos RPC call ../votes/listings is used to fetch the number of baker rolls and, ultimately, set baker status in the accounts tables. This RPC call returns no results for certain phases of governance like testing. This might have always been a bug or triggered by some relatively recent change in node behavior. Due to this, the accounts table shows incorrect data for is_baker in the accounts table.

Fixes:

• Change the logic for setting is_baker in the accounts tables to check the bakers table for a valid record.
• To set the 'rolls' value in the bakers tables, diving the 'staking_balance' field by a constant configured to 8,000.

Validation:

• For any well-known baker, there should be valid data in the accounts tables through all four cycles of governance.
• The new rolls values should match the value returned by the ../votes/listings RPC route for the proposal governance period.

[vishakh]

Wrong project.