fix: itests: Don't hang on exit in MineBlocksMustPost

[magik6k]

Proposed Changes

MineBlocksMustPost could hang during test cleanup, causing tests to randomly time out. The issue seems to be that we're waiting for a block to be mined, but the block mining logic has already shut down (this is quite racy, but happens a lot more it tests with very low block delays).

Additional Info

Happened in https://app.circleci.com/pipelines/github/filecoin-project/lotus/20105/workflows/1c498222-3542-4b64-bb14-5667927379e6/jobs/409257

Relevant goroutines:

goroutine 85 [semacquire, 28 minutes]:
sync.runtime_Semacquire(0xc0038ad250)
	/usr/local/go/src/runtime/sema.go:56 +0x45
sync.(*WaitGroup).Wait(0xc0038ad248)
	/usr/local/go/src/sync/waitgroup.go:130 +0x65
github.com/filecoin-project/lotus/itests/kit.(*BlockMiner).Stop(0xc0038ad230)
	/home/circleci/project/itests/kit/blockminer.go:324 +0x9a
testing.(*common).Cleanup.func1()
	/usr/local/go/src/testing/testing.go:901 +0xef
testing.(*common).runCleanup(0xc000592a80, 0x0, 0x0, 0x0)
	/usr/local/go/src/testing/testing.go:1007 +0x8c
testing.tRunner.func2(0xc000592a80)
	/usr/local/go/src/testing/testing.go:1187 +0x48
testing.tRunner(0xc000592a80, 0x4ae9e68)
	/usr/local/go/src/testing/testing.go:1197 +0x10e
created by testing.(*T).Run
	/usr/local/go/src/testing/testing.go:1238 +0x2b3



goroutine 894 [chan receive, 28 minutes]:
github.com/filecoin-project/lotus/itests/kit.(*BlockMiner).MineBlocksMustPost.func1(0xc0038ad230, 0x4d80178, 0xc001c42140, 0xf4240)
	/home/circleci/project/itests/kit/blockminer.go:195 +0x3c5
created by github.com/filecoin-project/lotus/itests/kit.(*BlockMiner).MineBlocksMustPost
	/home/circleci/project/itests/kit/blockminer.go:153 +0xd3

Checklist

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

• All commits have a clear commit message.
• The 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, INTERFACE BREAKING CHANGE, CONSENSUS BREAKING, build, chore, ci, docs,perf, refactor, revert, style, test
  • area: api, chain, state, vm, data transfer, market, mempool, message, block production, multisig, networking, paychan, proving, sealing, wallet, deps
• This PR has tests for new functionality or change in behaviour
• If new user-facing features are introduced, clear usage guidelines and / or documentation updates should be included in https://lotus.filecoin.io or Discussion Tutorials.
• CI is green

[codecov]

Codecov Report

Merging #8345 (42b2add) into master (18987f9) will decrease coverage by 0.01%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #8345      +/-   ##
==========================================
- Coverage   40.21%   40.19%   -0.02%     
==========================================
  Files         682      682              
  Lines       74425    74428       +3     
==========================================
- Hits        29929    29920       -9     
- Misses      39256    39270      +14     
+ Partials     5240     5238       -2     

Impacted Files	Coverage Δ
itests/kit/blockminer.go	69.56% <50.00%> (-0.61%)	⬇️
chain/actors/builtin/miner/diff.go	48.52% <0.00%> (-10.30%)	⬇️
markets/retrievaladapter/client_blockstore.go	62.50% <0.00%> (-6.25%)	⬇️
storage/wdpost_sched.go	75.49% <0.00%> (-3.93%)	⬇️
extern/storage-sealing/currentdealinfo.go	71.17% <0.00%> (-3.61%)	⬇️
chain/events/events_called.go	83.90% <0.00%> (-2.44%)	⬇️
chain/vm/vm.go	61.63% <0.00%> (-1.07%)	⬇️
extern/sector-storage/sched.go	84.77% <0.00%> (-0.83%)	⬇️
extern/storage-sealing/fsm.go	60.73% <0.00%> (-0.68%)	⬇️
extern/sector-storage/sched_worker.go	78.48% <0.00%> (-0.59%)	⬇️
... and 11 more