[SPARK-6070] [yarn] Remove unneeded classes from shuffle service jar.

These may conflict with the classes already in the NM. We shouldn't
be repackaging them.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #4820 from vanzin/SPARK-6070 and squashes the following commits:

871b566 [Marcelo Vanzin] The "d'oh how didn't I think of it before" solution.
3cba946 [Marcelo Vanzin] Use profile instead, so that dependencies don't need to be explicitly listed.
7a18a1b [Marcelo Vanzin] [SPARK-6070] [yarn] Remove unneeded classes from shuffle service jar.

network/yarn/pom.xml

@@ -33,6 +33,8 @@
   <url>http://spark.apache.org/</url>
   <properties>
     <sbt.project.name>network-yarn</sbt.project.name>
+    <!-- Make sure all Hadoop dependencies are provided to avoid repackaging. -->
+    <hadoop.deps.scope>provided</hadoop.deps.scope>
   </properties>
 
   <dependencies>
@@ -47,7 +49,6 @@
     <dependency>
       <groupId>org.apache.hadoop</groupId>
       <artifactId>hadoop-client</artifactId>
-      <scope>provided</scope>
     </dependency>
   </dependencies>