Avoid thread data race in connection_manager #6442

Job	Run time
pre-commit-hooks	1m 12s
clang-format	24s
shellcheck	18s
mypy	40s
isort	21s
lychee_IGNORED	25s
no-crlf	20s
black	33s
unused_names	18s
pydocstyle	28s
cppcheck	9m 31s
vale	34s
rstcheck	27s
forbidden_types	18s
pylint	43s
copyright_headers	24s
flake8	26s
sphinx-rtd	3m 30s
sphinx-conda	0s
build_macos (macos-latest, clang, openmp, mpi, python, gsl, ltdl, boost, hdf5, optimize, warning)	9m 18s
build_linux (ubuntu-22.04, gcc, boost, optimize, warning)	12m 10s
build_linux (ubuntu-22.04, gcc, optimize, warning)	10m 1s
build_linux (ubuntu-22.04, gcc, openmp, python, gsl, ltdl, boost, optimize, warning)	18m 41s
build_linux (ubuntu-22.04, gcc, mpi, python, gsl, ltdl, boost, optimize, warning)	19m 2s
build_linux (ubuntu-22.04, gcc, openmp, mpi, python, gsl, ltdl, boost, hdf5, sionlib, libneurosim...	30m 57s
	2h 1m 1s

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