[c-index-test] For the 'core' invocation, avoid running it under a new thread.
[c-index-test] For the 'core' invocation, avoid running it under a new thread.

It's unnecessary.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@295934 91177308-0d34-0410-b5e6-96231b3b80d8

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