support/testing/tests: fix flake8 warnings

support/testing/tests: fix flake8 warnings

Fixes the following flake8 warnings:

support/testing/tests/core/test_selinux.py:21:1: E302 expected 2 blank lines, found 1
support/testing/tests/core/test_selinux.py:38:1: E302 expected 2 blank lines, found 1
support/testing/tests/core/test_selinux.py:51:1: E302 expected 2 blank lines, found 1
support/testing/tests/core/test_selinux.py:62:1: E302 expected 2 blank lines, found 1
support/testing/tests/core/test_selinux.py:65:14: E127 continuation line over-indented for visual indent
support/testing/tests/init/test_systemd_selinux.py:53:1: E302 expected 2 blank lines, found 1
support/testing/tests/init/test_systemd_selinux.py:64:1: E302 expected 2 blank lines, found 1

Interestingly, the "continuation line over-indented for visual indent"
shows up only once, while the same pattern is there at multiple places
in the file. We fix all places with that over-indentation pattern.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>