[SPARK-13823][SPARK-13397][SPARK-13395][CORE] More warnings, StandardCharset follow up

## What changes were proposed in this pull request?

Follow up to https://github.com/apache/spark/pull/11657

- Also update `String.getBytes("UTF-8")` to use `StandardCharsets.UTF_8`
- And fix one last new Coverity warning that turned up (use of unguarded `wait()` replaced by simpler/more robust `java.util.concurrent` classes in tests)
- And while we're here cleaning up Coverity warnings, just fix about 15 more build warnings

## How was this patch tested?

Jenkins tests

Author: Sean Owen <sowen@cloudera.com>

Closes #11725 from srowen/SPARK-13823.2.

2 files changed, 3 insertions, 2 deletions

diff --git a/streaming/src/test/scala/org/apache/spark/streaming/scheduler/ReceiverTrackerSuite.scala b/streaming/src/test/scala/org/apache/spark/streaming/scheduler/ReceiverTrackerSuite.scala
index cfd7f86f84..7654bb2d03 100644
--- a/streaming/src/test/scala/org/apache/spark/streaming/scheduler/ReceiverTrackerSuite.scala
+++ b/streaming/src/test/scala/org/apache/spark/streaming/scheduler/ReceiverTrackerSuite.scala
@@ -105,7 +105,7 @@ class ReceiverTrackerSuite extends TestSuiteBase {
 }
 
 /** An input DStream with for testing rate controlling */
-private[streaming] class RateTestInputDStream(@transient _ssc: StreamingContext)
+private[streaming] class RateTestInputDStream(_ssc: StreamingContext)
   extends ReceiverInputDStream[Int](_ssc) {
 
   override def getReceiver(): Receiver[Int] = new RateTestReceiver(id)
diff --git a/streaming/src/test/scala/org/apache/spark/streaming/util/RateLimitedOutputStreamSuite.scala b/streaming/src/test/scala/org/apache/spark/streaming/util/RateLimitedOutputStreamSuite.scala
index 78fc344b00..6d9c80d992 100644
--- a/streaming/src/test/scala/org/apache/spark/streaming/util/RateLimitedOutputStreamSuite.scala
+++ b/streaming/src/test/scala/org/apache/spark/streaming/util/RateLimitedOutputStreamSuite.scala
@@ -18,6 +18,7 @@
 package org.apache.spark.streaming.util
 
 import java.io.ByteArrayOutputStream
+import java.nio.charset.StandardCharsets
 import java.util.concurrent.TimeUnit._
 
 import org.apache.spark.SparkFunSuite
@@ -34,7 +35,7 @@ class RateLimitedOutputStreamSuite extends SparkFunSuite {
     val underlying = new ByteArrayOutputStream
     val data = "X" * 41000
     val stream = new RateLimitedOutputStream(underlying, desiredBytesPerSec = 10000)
-    val elapsedNs = benchmark { stream.write(data.getBytes("UTF-8")) }
+    val elapsedNs = benchmark { stream.write(data.getBytes(StandardCharsets.UTF_8)) }
 
     val seconds = SECONDS.convert(elapsedNs, NANOSECONDS)
     assert(seconds >= 4, s"Seconds value ($seconds) is less than 4.")