out_stdout: Fix incomplete printing of traces #8486

Job	Run time
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, gcc)	12m 16s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, clang)	12m 16s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, gcc)	11m 26s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, clang)	11m 25s
run-ubuntu-unit-tests (-DFLB_SMALL=On, gcc)	11m 38s
run-ubuntu-unit-tests (-DFLB_SMALL=On, clang)	12m 19s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, gcc)	11m 46s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, clang)	11m 51s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, gcc)	11m 47s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, clang)	12m 5s
run-ubuntu-unit-tests (-DFLB_COVERAGE=On, gcc)	43m 33s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, gcc)	11m 29s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, clang)	11m 28s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, gcc)	11m 25s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, clang)	11m 31s
run-macos-unit-tests (-DFLB_JEMALLOC=Off)	11m 31s
run-macos-unit-tests (-DFLB_SANITIZE_MEMORY=On)	10m 49s
run-macos-unit-tests (-DFLB_SANITIZE_THREAD=On)	14m 0s
Unit tests (matrix)	1s
	4h 4m 36s

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