Merge branch 'sg/test-atexit'

Test framework update to more robustly clean up leftover files and processes after tests are done. * sg/test-atexit: t9811-git-p4-label-import: fix pipeline negation git p4 test: disable '-x' tracing in the p4d watchdog loop git p4 test: simplify timeout handling git p4 test: clean up the p4d cleanup functions git p4 test: use 'test_atexit' to kill p4d and the watchdog process t0301-credential-cache: use 'test_atexit' to stop the credentials helper tests: use 'test_atexit' to stop httpd git-daemon: use 'test_atexit` to stop 'git-daemon' test-lib: introduce 'test_atexit' t/lib-git-daemon: make sure to kill the 'git-daemon' process test-lib: fix interrupt handling with 'dash' and '--verbose-log -x'