[SPARK-13823][CORE][STREAMING][SQL] Always specify Charset in String <-> byte[] conversions (and remaining Coverity items)

## What changes were proposed in this pull request?

- Fixes calls to `new String(byte[])` or `String.getBytes()` that rely on platform default encoding, to use UTF-8
- Same for `InputStreamReader` and `OutputStreamWriter` constructors
- Standardizes on UTF-8 everywhere
- Standardizes specifying the encoding with `StandardCharsets.UTF-8`, not the Guava constant or "UTF-8" (which means handling `UnuspportedEncodingException`)
- (also addresses the other remaining Coverity scan issues, which are pretty trivial; these are separated into commit https://github.com/srowen/spark/commit/1deecd8d9ca986d8adb1a42d315890ce5349d29c )

## How was this patch tested?

Jenkins tests

Author: Sean Owen <sowen@cloudera.com>

Closes #11657 from srowen/SPARK-13823.

2 files changed, 5 insertions, 3 deletions

diff --git a/external/mqtt/src/main/scala/org/apache/spark/streaming/mqtt/MQTTInputDStream.scala b/external/mqtt/src/main/scala/org/apache/spark/streaming/mqtt/MQTTInputDStream.scala
index 079bd8a9a8..cbad6f7fe4 100644
--- a/external/mqtt/src/main/scala/org/apache/spark/streaming/mqtt/MQTTInputDStream.scala
+++ b/external/mqtt/src/main/scala/org/apache/spark/streaming/mqtt/MQTTInputDStream.scala
@@ -17,6 +17,8 @@
 
 package org.apache.spark.streaming.mqtt
 
+import java.nio.charset.StandardCharsets
+
 import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken
 import org.eclipse.paho.client.mqttv3.MqttCallback
 import org.eclipse.paho.client.mqttv3.MqttClient
@@ -75,7 +77,7 @@ class MQTTReceiver(
 
       // Handles Mqtt message
       override def messageArrived(topic: String, message: MqttMessage) {
-        store(new String(message.getPayload(), "utf-8"))
+        store(new String(message.getPayload(), StandardCharsets.UTF_8))
       }
 
       override def deliveryComplete(token: IMqttDeliveryToken) {
diff --git a/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTTestUtils.scala b/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTTestUtils.scala
index 26c6dc45d5..3680c13605 100644
--- a/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTTestUtils.scala
+++ b/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTTestUtils.scala
@@ -18,10 +18,10 @@
 package org.apache.spark.streaming.mqtt
 
 import java.net.{ServerSocket, URI}
+import java.nio.charset.StandardCharsets
 
 import scala.language.postfixOps
 
-import com.google.common.base.Charsets.UTF_8
 import org.apache.activemq.broker.{BrokerService, TransportConnector}
 import org.apache.commons.lang3.RandomUtils
 import org.eclipse.paho.client.mqttv3._
@@ -85,7 +85,7 @@ private[mqtt] class MQTTTestUtils extends Logging {
       client.connect()
       if (client.isConnected) {
         val msgTopic = client.getTopic(topic)
-        val message = new MqttMessage(data.getBytes(UTF_8))
+        val message = new MqttMessage(data.getBytes(StandardCharsets.UTF_8))
         message.setQos(1)
         message.setRetained(true)