fix: post worker sched: Don't check worker session in a busy loop

[magik6k]

Related Issues

Should help with #8362

Proposed Changes

On master the PoSt worker scheduler would check worker session at some interval, but the way the logic is implemented, it only sleeps if the check has failed. This results it a flood of requests between lotus-miner<->lotus-worker, which may lead to exhausting resources needed to make those http requests, leading to all sorts of random RPC-related issues.

Additional Info

Checklist

Before you mark the PR ready for review, please make sure that:

• Commits have a clear commit message.
• PR title is in the form of of <PR type>: <area>: <change being made>
  • example: fix: mempool: Introduce a cache for valid signatures
  • PR type: fix, feat, build, chore, ci, docs, perf, refactor, revert, style, test
  • area, e.g. api, chain, state, market, mempool, multisig, networking, paych, proving, sealing, wallet, deps
• New features have usage guidelines and / or documentation updates in
  • Lotus Documentation
  • Discussion Tutorials
• Tests exist for new functionality or change in behavior
• CI is green

[arajasek]

Nice improvement!