<!--- Verify first that your feature was not already discussed on GitHub -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### SUMMARY
<!--- Describe the new feature/improvement briefly below -->
This feature would implement a ClearSessions command for the Sessions category of redfish_command, to clear all active sessions.

##### ISSUE TYPE
- Feature Idea

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

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->
This command would help user to clear all active sessions.

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

```

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

response = self.get_request(self.root_uri + self.service_root)
        if response['ret'] is False:
            return response
        data = response['data']
        if 'UpdateService' not in data:
            return {'ret': False, 'msg': "UpdateService resource not found"}
        else:
            update = data["UpdateService"]["@odata.id"]
            self.update_uri = update
            response = self.get_request(self.root_uri + update)
            if response['ret'] is False:
                return response
            data = response['data']
            self.firmware_uri = self.software_uri = None
            if 'FirmwareInventory' in data:
                self.firmware_uri = data['FirmwareInventory'][u'@odata.id']
            if 'SoftwareInventory' in data:
                self.software_uri = data['SoftwareInventory'][u'@odata.id']
            return {'ret': True}
    def _find_chassis_resource(self):