tests: Define flags not present in Windows

Define flags S_IRWXO and S_IRWXG in torture_knownhosts_parsing.c when
building for Windows. These flags don't exist in Windows and are not
used.

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>