Add CERT file support in heat-keystone-setup-domain

Add below options to support ssl connection.
--insecure
--os-cacert
--os-cert
--os-key

Change-Id: I9d1fd07df783d7410ac3f51b5d4e8434d57182a4
Close-bug: #1387063
Using six.string_types for python3 compatible

For python3 compatible, using six.string_types instead of
basestring(). six.string_types represent basestring in
python2 and str in python3.

Change-Id: Ib4ba3d164f782601944023b99d6cc1ee2763ee85
Merge "Add CERT file support in heat-keystone-setup-domain"
Merge "Using six.string_types for python3 compatible"