[SPARK-14185][SQL][MINOR] Make indentation of debug log for generated code proper

## What changes were proposed in this pull request?

The indentation of debug log output by `CodeGenerator` is weird.
The first line of the generated code should be put on the next line of the first line of the log message.

```
16/03/28 11:10:24 DEBUG CodeGenerator: /* 001 */
/* 002 */ public java.lang.Object generate(Object[] references) {
/* 003 */   return new SpecificSafeProjection(references);
...
```

After this patch is applied, we get debug log like as follows.

```
16/03/28 10:45:50 DEBUG CodeGenerator:
/* 001 */
/* 002 */ public java.lang.Object generate(Object[] references) {
/* 003 */   return new SpecificSafeProjection(references);
...
```
## How was this patch tested?

Ran some jobs and checked debug logs.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #11990 from sarutak/fix-debuglog-indentation.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala

@@ -661,7 +661,7 @@ object CodeGenerator extends Logging {
     logDebug({
       // Only add extra debugging info to byte code when we are going to print the source code.
       evaluator.setDebuggingInformation(true, true, false)
-      formatted
+      s"\n$formatted"
     })
 
     try {