init: force fallocate_mode to none when fallocate is unsupported

init: force fallocate_mode to none when fallocate is unsupported

Commit 2c3e17be ("filesetup: add native fallocate") broke fio on Windows
because fallocate_mode wound up being set to 0 on platforms without any
type of fallocate. Work around this by forcing fallocate_mode to
FIO_FALLOCATE_NONE on such platforms.

This should address the issue mention in the mail
http://www.spinics.net/lists/fio/msg06085.html ("The commit 'filesetup:
add native fallocate' breaks on Cygwin").

Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com>