DAOS-14748 bio: race in stopping health monitor (#13500)

[NiuYawei]

Fix a race which could cause 'bdh_inflights' not being decreased when stopping health monitor on engine shutdown.

Before requesting gatekeeper:

• [ ] Two review approvals and any prior change requests have been resolved.
• [ ] Testing is complete and all tests passed or there is a reason documented in the PR why it should be force landed and forced-landing tag is set.
• [ ] Features: (or Test-tag*) commit pragma was used or there is a reason documented that there are no appropriate tags for this PR.
• [ ] Commit messages follows the guidelines outlined here.
• [ ] Any tests skipped by the ticket being addressed have been run and passed in the PR.

Gatekeeper:

• [ ] You are the appropriate gatekeeper to be landing the patch.
• [ ] The PR has 2 reviews by people familiar with the code, including appropriate owners.
• [ ] Githooks were used. If not, request that user install them and check copyright dates.
• [ ] Checkpatch issues are resolved. Pay particular attention to ones that will show up on future PRs.
• [ ] All builds have passed. Check non-required builds for any new compiler warnings.
• [ ] Sufficient testing is done. Check feature pragmas and test tags and that tests skipped for the ticket are run and now pass with the changes.
• [ ] If applicable, the PR has addressed any potential version compatibility issues.
• [ ] Check the target branch. If it is master branch, should the PR go to a feature branch? If it is a release branch, does it have merge approval in the JIRA ticket.
• [ ] Extra checks if forced landing is requested
  • [ ] Review comments are sufficiently resolved, particularly by prior reviewers that requested changes.
  • [ ] No new NLT or valgrind warnings. Check the classic view.
  • [ ] Quick-build or Quick-functional is not used.
• [ ] Fix the commit message upon landing. Check the standard here. Edit it to create a single commit. If necessary, ask submitter for a new summary.

[github-actions[bot]]

Bug-tracker data: Ticket title is 'container/per_server_fault_domain.py:PerServerFaultDomainTest.test_rf2_healthy - dmg system stop failed' Status is 'Awaiting backport' Labels: 'ci_impact,release/2.4,weekly_test' Job should run at elevated priority (1) https://daosio.atlassian.net/browse/DAOS-14748

[daosbuild1]

Test stage NLT on EL 8.8 completed with status UNSTABLE. https://build.hpdd.intel.com/job/daos-stack/job/daos//view/change-requests/job/PR-14008/1/testReport/