Incorrect field language is used when saving a new entity and translation is enabled (Entity translation)

Problem/Motivation

When saving a new entity using an entityreference field and the standard inline_entity_form widget the items are saved with the LANGUAGE_NONE langcode, and not the default language. E.g. 'en'. Like all other fields are. Entity translation is being used, but this is not the problem here.

Proposed resolution

Use field_language() in inline_entity_form_field_attach_submit() to get the correct langcode for the field, taking into account translation handlers etc..

Remaining tasks

User interface changes

None

API changes

None