Problem: warnings in release build

[tomtau]

warning: unused variable: `staking`
   --> chain-core/src/init/config.rs:239:13
    |
239 |         for staking in accounts.iter() {
    |             ^^^^^^^ help: consider prefixing with an underscore: `_staking`
    |
    = note: `#[warn(unused_variables)]` on by default

warning: unused variable: `minimal_required_staking`
   --> chain-abci/src/staking/table.rs:750:5
    |
750 |     minimal_required_staking: Coin,
    |     ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider prefixing with an underscore: `_minimal_required_staking`
    |
    = note: `#[warn(unused_variables)]` on by default

[yihuang]

I'll fix this in #1458