Dropdown Selection is wrong for translation node

Problem/Motivation

When you try to add a scheduled transition to a translation node (not the source one) the transition dropdown has wrong options. It always get the transitions options from the source node.

Steps to reproduce

• Create a node with a source language and publish it.
• Create a translation and create two or three revision with different state
• Go to the schedule transition page and add a new one
• Select a revision with a different state than publish

The dropdown menu will be fill with transition from publish to something else where it should be the one from the translation.

Proposed resolution

The ScheduledTransitionAddForm class should translate the entity before getting its transitions