Correct name of internal URL in endpoints and template

Base on the identity api speces [0][1], internal URL of a service
should be provided by 'internalURL' key instead of 'privateURL'.

[0] http://developer.openstack.org/api-ref-identity-v2.html
[1] http://developer.openstack.org/api-ref-identity-v3.html

Signed-off-by: Zhi Yan Liu <zhiyanl@cn.ibm.com>