tests/autotest_control.py: simple identation fix

Signed-off-by: Cleber Rosa <crosa@redhat.com>
virttest/utils_test.py: allow running autotest tests with standalone control files

This fix is needed when running tests on vms based on the autotest
client, when using control files that do not use job.run_test() and
similar calls. That is, the control files are standalone and do not
reference a client test.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
virt: introduce autotest_distro_detect test

This is a trivial test that exercises the recently added distro.py
module on autotest.

Signed-off-by: Cleber Rosa <crosa@redhat.com>