[SPARK-12249][SQL] JDBC non-equality comparison operator not pushed down.

[HyukjinKwon]

https://issues.apache.org/jira/browse/SPARK-12249
Currently != operator is not pushed down correctly.
I simply added a case for this.

[HyukjinKwon]

Several things to mention.

Firstly, I did not add the tests for it yet because pushed down filters are not correctly tested at the original test codes. I will add as soon as #10221 is merged.

Secondly, I just opened this PR without asking if it is really supposed to be supported. This is because I see the test codes intended to check this operator (which is not testing properly) and also I don't think there is any database not supporting this operator as it is a SQL Standard.

Lastly I tested this by adding a test locally with #10221.

[SparkQA]

Test build #47459 has finished for PR 10233 at commit 6cdd5f3.

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

[HyukjinKwon]

I updated the test for this since #10221 is merged.

[SparkQA]

Test build #47779 has finished for PR 10233 at commit 33f67e7.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):\n * case class WrapOption(child: Expression, optType: DataType)\n

[HyukjinKwon]

cc @rxin

[rxin]

Thanks - I've merged this into master.