[core] adjust time jump detection (fixes #3123)
[core] adjust time jump detection (fixes #3123)

adjust time jump detection to handle when server.max-workers is non-zero

x-ref:
  "child exit causes time jump false positive when server.max-workers is non-zero"
  https://redmine.lighttpd.net/issues/3123

gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4