out_stdout: Fix incomplete printing of traces #8412

Job	Run time
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, gcc)	12m 13s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, clang)	12m 14s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, gcc)	11m 36s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, clang)	11m 32s
run-ubuntu-unit-tests (-DFLB_SMALL=On, gcc)	11m 39s
run-ubuntu-unit-tests (-DFLB_SMALL=On, clang)	12m 27s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, gcc)	11m 47s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, clang)	11m 38s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, gcc)	11m 46s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, clang)	12m 6s
run-ubuntu-unit-tests (-DFLB_COVERAGE=On, gcc)	42m 54s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, gcc)	11m 36s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, clang)	11m 28s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, gcc)	11m 35s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, clang)	11m 44s
run-macos-unit-tests (-DFLB_JEMALLOC=Off)	11m 44s
run-macos-unit-tests (-DFLB_SANITIZE_MEMORY=On)	14m 31s
run-macos-unit-tests (-DFLB_SANITIZE_THREAD=On)	11m 56s
Unit tests (matrix)	1s
	4h 6m 27s

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