Commented Issue: Inner join instead of outer [960]

Inner join generated where an outer join is expected.

This happens when a join is made from T1 to T2 and then to T3 if relation T1-T2 is optional and T2-T3 is mandatory. Concrete example below.

__Details:__

Two tables (here T1=T2=Post, T3=Blog):

Blog
* Id (PK)
* Name

Post
* Id (PK)
* BlogId (FK to Blog.Id), Not NULL <== mandatory relation
* ParentPostId (FK to Post.Id), NULL <== optional relation
* Text

LINQ Query:
```
from p in db.Posts
where p.Id == 1
select new {p.Id, p.Text, p.ParentPost.Blog.Name}
```
EF5 SQL Statement (correct):
```
SELECT
[Limit1].[Id] AS [Id],
[Limit1].[Text] AS [Text],
[Extent3].[Name] AS [Name]
FROM (SELECT TOP (2) [Extent1].[Id] AS [Id], [Extent1].[ParentPostId] AS [ParentPostId], [Extent1].[Text] AS [Text]
FROM [dbo].[Post] AS [Extent1]
WHERE 1 = [Extent1].[Id] ) AS [Limit1]
LEFT OUTER JOIN [dbo].[Post] AS [Extent2] ON [Limit1].[ParentPostId] = [Extent2].[Id]
LEFT OUTER JOIN [dbo].[Blog] AS [Extent3] ON [Extent2].[BlogId] = [Extent3].[Id]
```
EF6 SQL Statement (wrong: inner join):

```
SELECT
[Limit1].[Id] AS [Id],
[Limit1].[Text] AS [Text],
[Extent3].[Name] AS [Name]
FROM (SELECT TOP (2) [Extent1].[Id] AS [Id], [Extent1].[ParentPostId] AS [ParentPostId], [Extent1].[Text] AS [Text]
FROM [dbo].[Post] AS [Extent1]
WHERE 1 = [Extent1].[Id] ) AS [Limit1]
LEFT OUTER JOIN [dbo].[Post] AS [Extent2] ON [Limit1].[ParentPostId] = [Extent2].[Id]
INNER JOIN [dbo].[Blog] AS [Extent3] ON [Extent2].[BlogId] = [Extent3].[Id]
```
The inner join is generated because Post.Blog is mandatory (BlogId is not null) but I expect an outer join because Post.ParentPost is optional (ParentPostId accepts null). As a result in EF6 no record is returned while EF5 returns one as expected.
Comments: Just checked: the issue is reproducing in the latest build, alpha3-20320