tests/internal: fix use-after-free for input_chunks test input_chunk_dropping_chunks.

[pwhelan]

Summary

There is a use-after-free bug in the internal test input_chunks, specifically in the sub-test input_chunk_dropping_chunks. This is caused by a premature and explicit freeing of all the chunks and explicit stopping of all the tasks by the test. This is done implicitly by either flb_stop or flb_destroy.

This PR simply eliminates this code to fix this potential use-after-free or double-free. This should make this test less flakey on macOS, as well as other operating systems.

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Testing
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• Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

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• Run local packaging test showing all targets (including any new ones) build.
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Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[pwhelan]

The only reasoning for this code would be to avoid a memory leak during the test which could cause it to fail with SANITIZE_ADDRESS=On. I therefore tested it with valgrind:

$ valgrind ./bin/flb-it-input_chunk input_chunk_dropping_chunks
==26247== Memcheck, a memory error detector
==26247== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==26247== Using Valgrind-3.23.0 and LibVEX; rerun with -h for copyright info
==26247== Command: ./bin/flb-it-input_chunk input_chunk_dropping_chunks
==26247==
Test input_chunk_dropping_chunks...             [2024/10/08 11:26:50] [error] [input chunk] fail to drop enough chunks in order to place new data coming from input plugin lib.0
[2024/10/08 11:26:50] [error] [output:http:http.0] no upstream connections available to 127.0.0.1:1
[2024/10/08 11:26:52] [error] [input chunk] fail to drop enough chunks in order to place new data coming from input plugin lib.0
[2024/10/08 11:26:52] [error] [output:http:http.0] no upstream connections available to 127.0.0.1:1
[2024/10/08 11:26:54] [error] [input chunk] fail to drop enough chunks in order to place new data coming from input plugin lib.0
[2024/10/08 11:26:54] [error] [output:http:http.0] no upstream connections available to 127.0.0.1:1
[2024/10/08 11:26:56] [error] [input chunk] fail to drop enough chunks in order to place new data coming from input plugin lib.0
[2024/10/08 11:26:56] [error] [output:http:http.0] no upstream connections available to 127.0.0.1:1
[2024/10/08 11:26:58] [error] [input chunk] fail to drop enough chunks in order to place new data coming from input plugin lib.0
[2024/10/08 11:26:58] [error] [output:http:http.0] no upstream connections available to 127.0.0.1:1
[2024/10/08 11:27:01] [error] [output:http:http.0] no upstream connections available to 127.0.0.1:1
[2024/10/08 11:27:01] [error] [engine] chunk '26247-1728397617.365742741.flb' cannot be retried: task_id=0, input=lib.0 > output=http.0
[ OK ]
==26247== Warning: invalid file descriptor -1 in syscall close()
SUCCESS: All unit tests have passed.
==26247==
==26247== HEAP SUMMARY:
==26247==     in use at exit: 0 bytes in 0 blocks
==26247==   total heap usage: 4,051 allocs, 4,051 frees, 1,957,249 bytes allocated
==26247==
==26247== All heap blocks were freed -- no leaks are possible
==26247==
==26247== For lists of detected and suppressed errors, rerun with: -s
==26247== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)