Check for the endmost target when chaining contains()

Check for the endmost target when chaining contains()

Fixed regression in association proxy due to :ticket:`3769`
(allow for chained any() / has()) where contains() against
an association proxy chained in the form
(o2m relationship, associationproxy(m2o relationship, m2o relationship))
would raise an error regarding the re-application of contains()
on the final link of the chain.

Change-Id: Iea51ce84c2c5a332416fff10b1ba0e676cf0bad7
Fixes: #4150