## What changes were proposed in this pull request?

This PR proposes to fix lint-check failures and javadoc8 break.

Few errors were introduced as below:

**lint-check failures**

```
[ERROR] src/test/java/org/apache/spark/network/TransportClientFactorySuite.java:[45,1] (imports) RedundantImport: Duplicate import to line 43 - org.apache.spark.network.util.MapConfigProvider.
[ERROR] src/main/java/org/apache/spark/unsafe/types/CalendarInterval.java:[255,10] (modifier) RedundantModifier: Redundant 'final' modifier.
```

**javadoc8**

```
[error] .../spark/sql/core/target/java/org/apache/spark/sql/streaming/StreamingQueryProgress.java:19: error: bad use of '>'
[error]  *                   "max" -> "2016-12-05T20:54:20.827Z"  // maximum event time seen in this trigger
[error]                             ^
[error] .../spark/sql/core/target/java/org/apache/spark/sql/streaming/StreamingQueryProgress.java:20: error: bad use of '>'
[error]  *                   "min" -> "2016-12-05T20:54:20.827Z"  // minimum event time seen in this trigger
[error]                             ^
[error] .../spark/sql/core/target/java/org/apache/spark/sql/streaming/StreamingQueryProgress.java:21: error: bad use of '>'
[error]  *                   "avg" -> "2016-12-05T20:54:20.827Z"  // average event time seen in this trigger
[error]                             ^
[error] .../spark/sql/core/target/java/org/apache/spark/sql/streaming/StreamingQueryProgress.java:22: error: bad use of '>'
[error]  *                   "watermark" -> "2016-12-05T20:54:20.827Z"  // watermark used in this trigger
[error]
```

## How was this patch tested?

Manually checked as below:

**lint-check failures**

```
./dev/lint-java
Checkstyle checks passed.
```

**javadoc8**

This seems hidden in the API doc but I manually checked after removing access modifier as below:

It looks not rendering properly (scaladoc).

![2016-12-16 3 40 34](https://cloud.githubusercontent.com/assets/6477701/21255175/8df1fe6e-c3ad-11e6-8cda-ce7f76c6677a.png)

After this PR, it renders as below:

- scaladoc
  ![2016-12-16 3 40 23](https://cloud.githubusercontent.com/assets/6477701/21255135/4a11dab6-c3ad-11e6-8ab2-b091c4f45029.png)

- javadoc
  ![2016-12-16 3 41 10](https://cloud.githubusercontent.com/assets/6477701/21255137/4bba1d9c-c3ad-11e6-9b88-62f1f697b56a.png)

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16307 from HyukjinKwon/lint-javadoc8.