iotests/297: Don't rely on distro-specific linter binaries

'pylint-3' is another Fedora-ism. Use "python3 -m pylint" or "python3 -m
mypy" to access these scripts instead. This style of invocation will
prefer the "correct" tool when run in a virtual environment.

Note that we still check for "pylint-3" before the test begins -- this
check is now "overly strict", but shouldn't cause anything that was
already running correctly to start failing. This is addressed by a
commit later in this series;
  'iotests/297: update tool availability checks'.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-id: 20211019144918.3159078-6-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

tests/qemu-iotests/297

@@ -71,14 +71,14 @@ def run_linters():
     sys.stdout.flush()
 
     env = os.environ.copy()
-    subprocess.run(('pylint-3', *files),
+    subprocess.run(('python3', '-m', 'pylint', *files),
                    env=env, check=False)
 
     print('=== mypy ===')
     sys.stdout.flush()
 
     env['MYPYPATH'] = env['PYTHONPATH']
-    p = subprocess.run(('mypy', *files),
+    p = subprocess.run(('python3', '-m', 'mypy', *files),
                        env=env,
                        check=False,
                        stdout=subprocess.PIPE,