README-service.md

In current implementation, when using `smb: yes`, only a small subset
of the attributes can be used in the playbook. This happened due the
use of `service_add_smb`, which adds a new service and does not modify
an existing one, and not coping with attributes not supported by this
IPA API call.

The implementation was modified so that a service with `smb: true` is
treated like any other service, which, in effect, simplified and fixed
service search, and allowed for the use of the same attributes as with
any service. Although simplified, when using `smb: true` an extra
query is done against the LDAP server, as a second `service_show` is
performed.

Tests have been updated to reflect the new imprlementation.