Merge branch 'ab/pager-exit-log'

When a pager spawned by us exited, the trace log did not record its
exit status correctly, which has been corrected.

* ab/pager-exit-log:
  pager: properly log pager exit code when signalled
  run-command: add braces for "if" block in wait_or_whine()
  pager: test for exit code with and without SIGPIPE
  pager: refactor wait_for_pager() function