SPARK-6532 [BUILD] LDAModel.scala fails scalastyle on Windows

Use standard UTF-8 source / report encoding for scalastyle

Author: Sean Owen <sowen@cloudera.com>

Closes #5211 from srowen/SPARK-6532 and squashes the following commits:

16a33e5 [Sean Owen] Use standard UTF-8 source / report encoding for scalastyle

pom.xml

@@ -1452,7 +1452,8 @@
           <testSourceDirectory>${basedir}/src/test/scala</testSourceDirectory>
           <configLocation>scalastyle-config.xml</configLocation>
           <outputFile>scalastyle-output.xml</outputFile>
-          <outputEncoding>UTF-8</outputEncoding>
+          <inputEncoding>${project.build.sourceEncoding}</inputEncoding>
+          <outputEncoding>${project.reporting.outputEncoding}</outputEncoding>
         </configuration>
         <executions>
           <execution>