test/py: net_boot: fix comment

If env__pxe_boot_test_skip is not present, it defaults to True not
False. Therefore fix the comment.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
1 file changed