<!--- 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 -->

d = data.get('Links', {})
            elif '.' in sub:  
                p, sub = sub.split('.')
                u = data.get(p, {}).get('@odata.id')
                if u:
                    r = self.get_request(self.root_uri + u)
                    if r['ret']:
                        d = r['data']
                if not d:
                    continue
            else:  
                d = data
            health[sub] = []
            self.get_health_subsystem(sub, d, health)
            if not health[sub]:
                del health[sub]
        result["entries"] = health
        return result
    def get_system_health_report(self, systems_uri):
        subsystems = ['Processors', 'Memory', 'SimpleStorage', 'Storage',
                      'EthernetInterfaces', 'NetworkInterfaces.NetworkPorts',
                      'NetworkInterfaces.NetworkDeviceFunctions']
        return self.get_health_report('System', systems_uri, subsystems)
    def get_multi_system_health_report(self):
        return self.aggregate_systems(self.get_system_health_report)
    def get_chassis_health_report(self, chassis_uri):
        subsystems = ['Power.PowerSupplies', 'Thermal.Fans',
                      'Links.PCIeDevices']
        return self.get_health_report('Chassis', chassis_uri, subsystems)
    def get_multi_chassis_health_report(self):