I am having similar problem. So for testing, I have added a sleep of 1 or 2 sec. between obtaining authenticated SAML token from SSO and login with vCD through ssoLogin(). That fixed the issue.
Anyways, its worth trying this solution. Try adding NTP server through 'Time Configuration' on host and make sure the vCenter and vCD has 'Synchronize guest time with host' selected. (Edit Settings --> Options --> VMware Tools)