upgrade deferred loader to regular loader if refresh_state

upgrade deferred loader to regular loader if refresh_state

Fixed issue where deferred polymorphic loading of attributes from a
joined-table inheritance subclass would fail to populate the attribute
correctly if the :func:`_orm.load_only` option were used to originally
exclude that attribute, in the case where the load_only were descending
from a relationship loader option.  The fix allows that other valid options
such as ``defer(..., raiseload=True)`` etc. still function as expected.

Fixes: #7304
Change-Id: I58b7ce7c450bcc52d2f0c9bfbcb4d747463ee9b2