test/py: efi_secboot: apply autopep8

Python's autopep8 can automatically correct some of warnings from pylint
and rewrite the code in a pretty print format. So just do it.

Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>