<!--- Verify first that your issue is not already reported on GitHub -->
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##### SUMMARY
<!--- Explain the problem briefly below -->
Ansible documents a fact_caching_prefix option for the jsonfile cache plugin. It does not appear to do anything. Also, the fact_caching_connection option is documented as `_uri` rather than `_connection`.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
jsonfile

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.8
  config file = /home/mark/src/ansible/ansible2/ansible.cfg
  configured module search path = [u'/home/mark/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /home/mark/src/ansible-playground/venv-2.9/local/lib/python2.7/site-packages/ansible
  executable location = /home/mark/src/ansible-playground/venv-2.9/bin/ansible
  python version = 2.7.12 (default, Oct  8 2019, 14:14:10) [GCC 5.4.0 20160609]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
Ubuntu

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

<!--- HINT: You can paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->


##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below

```

cachefile = "%s/%s" % (self._cache_dir, key)
        if key in self._cache:
            return True
        if self.has_expired(key):
            return False
        try:
            os.stat(cachefile)
            return True
        except (OSError, IOError) as e:
            if e.errno == errno.ENOENT:
                return False
            else:
                display.warning("error in '%s' cache plugin while trying to stat %s : %s" % (self.plugin_name, cachefile, to_bytes(e)))
    def delete(self, key):
        try:
            del self._cache[key]
        except KeyError:
            pass
        try:
            os.remove("%s/%s" % (self._cache_dir, key))
        except (OSError, IOError):
            pass  
    def flush(self):
        self._cache = {}
        for key in self.keys():
            self.delete(key)
    def copy(self):