Arrange the bybusyness logic and prevent bad busy values. #25

Job	Run time
Empty APLOGNO() test	56s
Default	5m 8s
All-static modules	3m 55s
Prefork MPM, all-modules (except cgid)	4m 57s
Worker MPM, all-modules	5m 55s
Shared MPMs, all-modules	5m 56s
Event MPM, all-modules, mod_cgid only	4m 28s
Event MPM, all-modules, no CMSG_DATA	4m 37s
Default, all-modules + install	4m 27s
Default, all-modules, random test order	5m 10s
GCC 10 maintainer-mode w/-Werror, install + VPATH	3m 30s
All-modules, APR 1.7.4, APR-util 1.6.3	4m 50s
APR 1.8.x, APR-util 1.7.x	6m 50s
Pool-debug	8m 48s
Shared MPMs (event), pool-debug, SSL/TLS variants	15m 47s
Shared MPMs (worker), pool-debug, SSL/TLS variants	15m 9s
Shared MPMs (prefork), pool-debug, SSL/TLS variants	16m 51s
litmus WebDAV tests	2m 46s
Regenerate ap_expr	1m 57s
APR 1.7.4, APR-util 1.6.3, LDAP	4m 10s
APR trunk thread debugging	4m 51s
UBSan	6m 39s
ASan	7m 35s
ASan, pool-debug	10m 4s
HTTP/2 test suite	12m 46s
MOD_TLS test suite	5m 39s
	2h 53m 41s

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