Add security service DB model and API.

Add support for managing security services information.

User will be able to create description for services
such as ldap, kerberos and active directory.
Security service record will contain type of service
(kerberos, ldap or ad), ip address of dns server, security
service server hostname or ip, domain, sid (security identifier)
and other auxiliary data.

Partially implements bp: join-tenant-network

Change-Id: I50e1f96496a40840aad97b77024a11302a1dd997