Fix shibboleth invitation user mapper in multi repository env

In org.nuxeo.shibboleth.invitation.ShibbolethUserMapper#getOrCreateAndUpdateNuxeoPrincipal(java.lang.Object, boolean, boolean, java.util.Map<java.lang.String,java.io.Serializable>), the session to update ACL for an invited user is bound the default repository. We should be able to use the actual session (by adding service in User Mapper)