[storage] fix flaky pruner test
[storage] fix flaky pruner test

The pruner initial seek result should be substituted by 1, otherwise it confuses the test.

Closes: #7215

aptos-labs/aptos-core,libra/libra,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core