Add application_credential as a CADF type
Add application_credential as a CADF type

This change adds 'application_credential' as a
'data/security/credential' CADF type, so that upon creating the CADF
payload the target URI is set to a valid type and not to 'unknown'.

Change-Id: I201ce5983409d99cbcaf0f0081be857b3194fa79

mahak/keystone,openstack/keystone,mahak/keystone,openstack/keystone,openstack/keystone,mahak/keystone