virttest: supress pylint false negatives

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
virttest.utils_misc_unittest: PEP8 Fixes
virttest: PEP8 Fixes

Change the 'if not condition is None' for the equivalent
and more correct 'if condition is not None'.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
virttest: Mass PEP8 changes

Change the expression 'not element in list' to the more
correct 'element not in list'.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>