Populate TrustDomain's domain attribute.

        This entails an inspection of each device's certificate-authority
        devices in its trust domain and recording them. After which, we
        get a dictionary of who trusts who in the domain.

def _populate_domain(self):
        '''Populate TrustDomain's domain attribute.

        This entails an inspection of each device's certificate-authority
        devices in its trust domain and recording them. After which, we
        get a dictionary of who trusts who in the domain.
        '''

        self.domain = {}
        for device in self.devices:
            device_name = get_device_info(device).name
            ca_devices = \
                device.tm.cm.trust_domains.trust_domain.load(
                    name='Root'
                ).caDevices
            self.domain[device_name] = [
                d.replace('/%s/' % self.partition, '') for d in ca_devices
            ]