tests: avoid test-hup hanging on AIX...
tests: avoid test-hup hanging on AIX
test-hup hangs on AIX. Under ksh89 on AIX (the default shell),
echo Hello; while [ ! -s not-there ]; do true; done
produces no output while the loop executes. Replacing 'true' with 'sleep 0'
fixes, as does using a less broken shell. ksh93 is fine.
Update check-code.py to look for this, and make same change in test-serve.t.
In fact test-serve works fine, probably because of additional commands between
echo and the loop, but that's a subtlety not easy to test for.
