Merge branch 'jk/test-annoyances' into maint

Test fixes.

* jk/test-annoyances:
  t5551: make EXPENSIVE test cheaper
  t5541: move run_with_cmdline_limit to test-lib.sh
  t: pass GIT_TRACE through Apache
  t: redirect stderr GIT_TRACE to descriptor 4
  t: translate SIGINT to an exit