Implement Locking/Unlocking adom

[dasTor]

Hey,

thanks for your library. I am currently using an extension, which others may also use:

def un_or_lock_adom(method):
    url = "/dvmdb/adom/{}/workspace/{}".format(fortimngr.adom, method)

    payload = \
        {
            "method": "exec",
            "params":
                [
                    {
                        "url": url
                    }
                ],
        }

    fortimngr.custom_api(payload)

def lock_adom():
    return un_or_lock_adom("lock")

def unlock_adom():
    return un_or_lock_adom("unlock")

Maybe the lock and unlock methods would be useful on the FortiManager object?