[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.

1 files changed, 0 insertions, 2 deletions

diff --git a/sql/core/src/test/java/test/org/apache/spark/sql/sources/JavaSaveLoadSuite.java b/sql/core/src/test/java/test/org/apache/spark/sql/sources/JavaSaveLoadSuite.java
index 0f9e453d26..9e65158eb0 100644
--- a/sql/core/src/test/java/test/org/apache/spark/sql/sources/JavaSaveLoadSuite.java
+++ b/sql/core/src/test/java/test/org/apache/spark/sql/sources/JavaSaveLoadSuite.java
@@ -40,7 +40,6 @@ public class JavaSaveLoadSuite {
   private transient JavaSparkContext sc;
   private transient SQLContext sqlContext;
 
-  String originalDefaultSource;
   File path;
   Dataset<Row> df;
 
@@ -57,7 +56,6 @@ public class JavaSaveLoadSuite {
     sqlContext = new SQLContext(_sc);
     sc = new JavaSparkContext(_sc);
 
-    originalDefaultSource = sqlContext.conf().defaultDataSourceName();
     path =
       Utils.createTempDir(System.getProperty("java.io.tmpdir"), "datasource").getCanonicalFile();
     if (path.exists()) {