shell: fix lost log messages during initialization #10153

Job	Run time
validate commits	8s
python linting	33s
Generate build matrix	7s
spelling	6s
bookworm - test-install	12m 51s
bookworm - 32 bit	13m 15s
noble - test-install	13m 19s
el9 - test-install	12m 40s
alpine - test-install	13m 1s
fedora40 - test-install	12m 2s
jammy - test-install	12m 16s
focal - py3.8	17m 4s
bookworm - gcc-12,content-s3,distcheck	19m 56s
fedora40 - clang-18	17m 2s
coverage	23m 21s
el8 - ascii	20m 6s
el8 - test-install	13m 11s
el8 - system,coverage	7m 8s
inception	21m 33s
flux-pmix check	13m 26s
flux-pam check	4m 19s
flux-accounting check	4m 39s
macos build only	3m 43s
flux-sched check	6m 53s
Generate docker manifest	1s
	4h 22m 40s

Provide feedback