call correct mkdir when trying to create /etc/rhsm/facts

os.path has no mkdir, but os does.

traceback without the patch:

    Traceback (most recent call last):
      File "/bin/leapp", line 11, in <module>
        load_entry_point('leapp==0.16.0', 'console_scripts', 'leapp')()
      File "/usr/lib/python3.6/site-packages/leapp/cli/__init__.py", line 45, in main
        cli.command.execute('leapp version {}'.format(VERSION))
      File "/usr/lib/python3.6/site-packages/leapp/utils/clicmd.py", line 111, in execute
        args.func(args)
      File "/usr/lib/python3.6/site-packages/leapp/utils/clicmd.py", line 133, in called
        self.target(args)
      File "/usr/lib/python3.6/site-packages/leapp/cli/commands/upgrade/breadcrumbs.py", line 170, in wrapper
        breadcrumbs.save()
      File "/usr/lib/python3.6/site-packages/leapp/cli/commands/upgrade/breadcrumbs.py", line 116, in save
        self._save_rhsm_facts(doc['activities'])
      File "/usr/lib/python3.6/site-packages/leapp/cli/commands/upgrade/breadcrumbs.py", line 64, in _save_rhsm_facts
        os.path.mkdir('/etc/rhsm/facts')
    AttributeError: module 'posixpath' has no attribute 'mkdir'

commands/upgrade/breadcrumbs.py

@@ -61,7 +61,7 @@ def _save_rhsm_facts(self, activities):
             if not os.path.exists('/etc/rhsm'):
                 # If there's no /etc/rhsm folder just skip it
                 return
-            os.path.mkdir('/etc/rhsm/facts')
+            os.mkdir('/etc/rhsm/facts')
         try:
             with open('/etc/rhsm/facts/leapp.facts', 'w') as f:
                 json.dump(_flattened({