Merge branch 'jk/t7006-sigpipe-tests-fix'

Merge branch 'jk/t7006-sigpipe-tests-fix'

The function to cull a child process and determine the exit status
had two separate code paths for normal callers and callers in a
signal handler, and the latter did not yield correct value when the
child has caught a signal.  The handling of the exit status has
been unified for these two code paths.  An existing test with
flakiness has also been corrected.

* jk/t7006-sigpipe-tests-fix:
  t7006: simplify exit-code checks for sigpipe tests
  t7006: clean up SIGPIPE handling in trace2 tests
  run-command: unify signal and regular logic for wait_or_whine()