Fix lint-check failures and javadoc8 break (apache#187)

* [MINOR][BUILD] Fix lint-check failures and javadoc8 break

## 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 apache#16307 from HyukjinKwon/lint-javadoc8.

(cherry picked from commit ed84cd0)

* Bring back needed import

common/unsafe/src/main/java/org/apache/spark/unsafe/types/CalendarInterval.java

@@ -252,7 +252,7 @@ public static long parseSecondNano(String secondNano) throws IllegalArgumentExce
   public final int months;
   public final long microseconds;
 
-  public final long milliseconds() {
+  public long milliseconds() {
     return this.microseconds / MICROS_PER_MILLI;
   }
 

sql/core/src/main/scala/org/apache/spark/sql/streaming/progress.scala

@@ -68,12 +68,12 @@ class StateOperatorProgress private[sql](
  *                incremented.
  * @param durationMs The amount of time taken to perform various operations in milliseconds.
  * @param eventTime Statistics of event time seen in this batch. It may contain the following keys:
- *                 {
+ *                 {{{
  *                   "max" -> "2016-12-05T20:54:20.827Z"  // maximum event time seen in this trigger
  *                   "min" -> "2016-12-05T20:54:20.827Z"  // minimum event time seen in this trigger
  *                   "avg" -> "2016-12-05T20:54:20.827Z"  // average event time seen in this trigger
  *                   "watermark" -> "2016-12-05T20:54:20.827Z"  // watermark used in this trigger
- *                 }
+ *                 }}}
  *                 All timestamps are in ISO8601 format, i.e. UTC timestamps.
  * @param stateOperators Information about operators in the query that store state.
  * @param sources detailed statistics on data being read from each of the streaming sources.