Add filter to xxx2Many fields
The domain is not taken in account in [1] and [2] and the xxx2Many fields return incorrect values because they doesn't filer by domain.
I attached a review that adds a test for this use case.
Both test fails with a validation domain, because the second field (which have a domain) return the invalid values for the current model.
[1] http://hg.tryton.org/trytond/file/c427c593baf0/trytond/model/fields/one2many.py#l78
[2] http://hg.tryton.org/trytond/file/c427c593baf0/trytond/model/fields/many2many.py#l61