'Hunts for a server on the Dell backend by instance_name.
The instance_name is the same as the server\'s HBA.  This is the  IQN or
WWN listed in the connector.  If found, the server the HBA is attached
to, if any, is returned.
:param instance_name: instance_name is a FC WWN or iSCSI IQN from
the connector.  In cinder a server is identified
by its HBA.
:param ssn: Storage center to search.
:returns: Dell server object or None.'

def find_server(self, instance_name, ssn=(-1)):

    ssn = self._vet_ssn(ssn)
    scserver = None
    hba = self._find_serverhba(instance_name, ssn)
    if ((hba is not None) and (hba.get('server') is not None)):
        pf = self._get_payload_filter()
        pf.append('scSerialNumber', ssn)
        pf.append('instanceId', self._get_id(hba['server']))
        r = self.client.post('StorageCenter/ScServer/GetList', pf.payload)
        if self._check_result(r):
            scserver = self._first_result(r)
    if (scserver is None):
        LOG.debug('Server    (%s)    not    found.', instance_name)
    return scserver
