<!--- Verify first that your feature was not already discussed on GitHub -->
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##### 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 -->

protocol_services = ['SNMP', 'VirtualMedia', 'Telnet', 'SSDP', 'IPMI', 'SSH',
                             'KVMIP', 'NTP', 'HTTP', 'HTTPS', 'DHCP', 'DHCPv6', 'RDP',
                             'RFB']
        protocol_state_onlist = ['true', 'True', True, 'on', 1]
        protocol_state_offlist = ['false', 'False', False, 'off', 0]
        payload = {}
        for service_name in manager_services.keys():
            if service_name not in protocol_services:
                return {'ret': False, 'msg': "Service name %s is invalid" % service_name}