Do not use yield_per when eager loading is used

In our case using yield_per ended with duplicated rows.
SQLAlchemy docs do not recommend using it when joinedload
or subqueryload are used. In version 1.0 SQLAlchemy will raise
Exception http://docs.sqlalchemy.org/en/latest/changelog/migration_10.html#joined-subquery-eager-loading-explicitly-disallowed-with-yield-per

Closes-bug: 1382627
blueprint 100-nodes-support

Change-Id: I1d9f3c14cba55eda0a0c9176ac745ed28a84476c
Merge "Do not use yield_per when eager loading is used"