fix: [cherry-pick]Replace gettid() with syscall(SYS_gettid)

[xige-16]

pr: #396
/kind bug
issue: #696

[sre-ci-robot]

Welcome @xige-16! It looks like this is your first PR to zilliztech/knowhere 🎉

[mergify]

@xige-16 🔍 Important: PR Classification Needed!

For efficient project management and a seamless review process, it's essential to classify your PR correctly. Here's how:

1. If you're fixing a bug, label it as kind/bug.
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[mergify]

@xige-16 e2e jenkins job failed, comment /run-e2e can trigger the job again.

[alexanderguzhva]

/lgtm

[alexanderguzhva]

/run-e2e

[liliu-z]

/kind improvement

[xige-16]

/run-e2e

[xige-16]

e2e is as unstable as milvus. haha.

[xige-16]

/run-e2e

[liliu-z]

e2e is as unstable as milvus. haha.

Looks like it is not about stability but some E2E issue. Plz take a check today. @cydrain

[mergify]

@xige-16 e2e jenkins job failed, comment /run-e2e can trigger the job again.

[cydrain]

/lgtm
/approve

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cydrain, xige-16

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