Fix type error in TornadoImporter

[dwoz]

What does this PR do?

Fixes tracebacks in salt loader because the find_module method of TornadoImporter required 3 arguments, path should default to None.

Traceback (most recent call last):
  File "/tmp/kitchen/testing/salt/loader.py", line 1607, in _load_module
    mod = imp.load_module(mod_namespace, fn_, fpath, desc)
  File "/tmp/kitchen/testing/salt/grains/esxi.py", line 16, in <module>
    import salt.modules.vsphere
  File "/tmp/kitchen/testing/salt/modules/vsphere.py", line 222, in <module>
    import jsonschema
  File "/tmp/kitchen/testing/.nox/runtests-parametrized-2-7-coverage-true-crypto-none-transport-zeromq/lib/python2.7/site-packages/jsonschema/__init__.py", line 18, in <module>
    from jsonschema.validators import (
  File "/tmp/kitchen/testing/.nox/runtests-parametrized-2-7-coverage-true-crypto-none-transport-zeromq/lib/python2.7/site-packages/jsonschema/validators.py", line 170, in <module>
    meta_schema=_utils.load_schema("draft3"),
  File "/tmp/kitchen/testing/.nox/runtests-parametrized-2-7-coverage-true-crypto-none-transport-zeromq/lib/python2.7/site-packages/jsonschema/_utils.py", line 57, in load_schema
    data = pkgutil.get_data('jsonschema', "schemas/{0}.json".format(name))
  File "/usr/lib64/python2.7/pkgutil.py", line 578, in get_data
    loader = get_loader(package)
  File "/usr/lib64/python2.7/pkgutil.py", line 464, in get_loader
    return find_loader(fullname)
  File "/usr/lib64/python2.7/pkgutil.py", line 475, in find_loader
    loader = importer.find_module(fullname)
TypeError: find_module() takes exactly 3 arguments (2 given)

What issues does this PR fix or reference?

#56063

Tests written?

Yes

Commits signed with GPG?

Yes

[tutume]

I'm not sure if it is related, but the behaviour matches.

I'm doing some tests and have 2 clean install, I did both today based on repo.saltstack.com orientation of Python 3 version for eath OS ,1 Ubuntu 18.04 and 2 Windows 10 Pro 1909.

The issue happens where I already have python installed (Ubuntu and one of the Windows 10's)
The second Windows 10, without python preinstalled, runs with no issue at all.