'Creates folder under parent.
This can create both to server and volume folders.  The REST url
sent in defines the folder type being created on the Dell Storage
Center backend.
:param url: This is the Dell SC rest url for creating the specific
(server or volume) folder type.
:param parent: The instance ID of this folder\'s parent folder.
:param folder: The folder name to be created.  This is one level deep.
:returns: The REST folder object.'

def _create_folder(self, url, parent, folder, ssn=(-1)):

    ssn = self._vet_ssn(ssn)
    scfolder = None
    payload = {}
    payload['Name'] = folder
    payload['StorageCenter'] = ssn
    if (parent != ''):
        payload['Parent'] = parent
    payload['Notes'] = self.notes
    r = self.client.post(url, payload, True)
    if self._check_result(r):
        scfolder = self._first_result(r)
    return scfolder
