tests: redirect all cmn_err output to stderr and flush it
tests: redirect all cmn_err output to stderr and flush it

Usually stderr is unbuffered, but these are tests so (1) we expect errors,
(2) we really don't want to lose them, and (3) performance isn't that
important.

Signed-off-by: Josef 'Jeff' Sipek <a620f141433c70aa9e43778305a6c68cbfadfb25@josefsipek.net>

jeffpc/libjeffpc,jeffpc/libjeffpc,jeffpc/libjeffpc,jeffpc/libjeffpc