[SPARK-9113][SQL] enable analysis check code for self join

[cloud-fan]

The check was unreachable before, as case operator: LogicalPlan catches everything already.

[marmbrus]

I think we do want to throw an error message here. We handle all case correctly today, but if we add new operator it could break and the result of planning a query with conflicting attributes is usually very confusing.

[SparkQA]

Test build #37571 has finished for PR 7449 at commit 5493aea.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #37575 has finished for PR 7449 at commit 07385df.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #37586 has finished for PR 7449 at commit 2bb6637.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[marmbrus]

Thanks for fixing this! Merging to master.