simplify _get_boot_file_path #451

Job	Run time
bookworm armv7 / build	1m 25s
bullseye armv7 / build	1m 30s
bookworm armv7 / test (run_install_common.sh)	16m 56s
bookworm armv7 / test (run_install_faststartup.sh)	13m 39s
bookworm armv7 / test (run_install_webapp_local.sh)	23m 26s
bookworm armv7 / test (run_install_webapp_download.sh)	16m 1s
bookworm armv7 / test (run_install_libzmq_local.sh)	27m 52s
bullseye armv7 / test (run_install_common.sh)	13m 16s
bullseye armv7 / test (run_install_faststartup.sh)	9m 47s
bullseye armv7 / test (run_install_webapp_local.sh)	20m 29s
bullseye armv7 / test (run_install_webapp_download.sh)	14m 46s
bullseye armv7 / test (run_install_libzmq_local.sh)	23m 28s
bullseye armv7 / cleanup	4s
bookworm armv7 / cleanup	2s
	3h 2m 41s

Provide feedback