selftests: remove shebang from selftest files

Self test files used to be executable, but that changed on 143b574c.
So, it doesn't make much sense to keep the shebangs + python commands
on them.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

selftests/all/doc/doc_build_test.py

-#!/usr/bin/python
 """
 Build documentation and report whether we had warning/error messages.
 

selftests/all/functional/avocado/basic_tests.py

-#!/usr/bin/env python
-
 import json
 import unittest
 import os

selftests/all/functional/avocado/export_variables_tests.py

-#!/usr/bin/env python
-
 import os
 import sys
 import shutil

selftests/all/functional/avocado/gdb_tests.py

-#!/usr/bin/env python
-
 import os
 import sys
 import unittest

selftests/all/functional/avocado/journal_tests.py

-#!/usr/bin/env python
-
 import unittest
 import os
 import sys

selftests/all/functional/avocado/loader_tests.py

-#!/usr/bin/env python
-
 import os
 import sys
 import unittest

selftests/all/functional/avocado/output_check_tests.py

-#!/usr/bin/env python
-
 import os
 import shutil
 import sys

selftests/all/functional/avocado/output_tests.py

-#!/usr/bin/env python
-
 import json
 import tempfile
 import unittest

selftests/all/functional/avocado/standalone_tests.py

-#!/usr/bin/env python
-
 import unittest
 import os
 import sys

selftests/all/functional/avocado/utils_tests.py

-#!/usr/bin/env python
-
 import os
 import sys
 import unittest

selftests/all/functional/avocado/wrapper_tests.py

-#!/usr/bin/env python
-
 import os
 import sys
 import unittest

selftests/all/unit/avocado/archive_unittest.py

-#!/usr/bin/env python
-
 import unittest
 import tempfile
 import os

selftests/all/unit/avocado/datadir_unittest.py

-#!/usr/bin/env python
-
 import unittest
 import os
 import sys

selftests/all/unit/avocado/jsonresult_unittest.py

-#!/usr/bin/env python
-
 import unittest
 import os
 import sys

selftests/all/unit/avocado/loader_unittest.py

-#!/usr/bin/env python
-
 import os
 import sys
 import unittest

selftests/all/unit/avocado/multiplexer_unittest.py

-#!/usr/bin/env python
-
 import unittest
 
 from avocado import multiplexer

selftests/all/unit/avocado/plugins_unittest.py

-#!/usr/bin/env python
-
 import sys
 import os
 import unittest

selftests/all/unit/avocado/remote_unittest.py

-#!/usr/bin/env python
-
 import unittest
 import os
 import sys

selftests/all/unit/avocado/settings_unittest.py

-#!/usr/bin/env python
-
 import unittest
 import os
 import sys

selftests/all/unit/avocado/sysinfo_unittest.py

-#!/usr/bin/env python
-
 import os
 import sys
 import unittest

selftests/all/unit/avocado/test_unittest.py

-#!/usr/bin/env python
-
 import unittest
 import os
 import shutil

selftests/all/unit/avocado/tree_unittest.py

-#!/usr/bin/env python
-
 import copy
 import unittest
 

selftests/all/unit/avocado/utils_params_unittest.py

-#!/usr/bin/python
-
 import unittest
 
 from avocado.utils import params

selftests/all/unit/avocado/utils_process_unittest.py

-#!/usr/bin/python
-
 import unittest
 
 from avocado import runtime

selftests/all/unit/avocado/vm_unittest.py

-#!/usr/bin/env python
-
 import unittest
 import os
 import sys

selftests/all/unit/avocado/xunit_unittest.py

-#!/usr/bin/env python
-
 import argparse
 import unittest
 import os