[HOT FIX] Make distribution fails

This was added by me in https://github.com/apache/spark/commit/61a5cced049a8056292ba94f23fa7bd040f50685. The real fix will be added in [SPARK-4281](https://issues.apache.org/jira/browse/SPARK-4281).

Author: Andrew Or <andrew@databricks.com>

Closes #3145 from andrewor14/fix-make-distribution and squashes the following commits:

c78be61 [Andrew Or] Hot fix make distribution

make-distribution.sh

@@ -181,9 +181,6 @@ echo "Spark $VERSION$GITREVSTRING built for Hadoop $SPARK_HADOOP_VERSION" > "$DI
 # Copy jars
 cp "$FWDIR"/assembly/target/scala*/*assembly*hadoop*.jar "$DISTDIR/lib/"
 cp "$FWDIR"/examples/target/scala*/spark-examples*.jar "$DISTDIR/lib/"
-cp "$FWDIR"/network/yarn/target/scala*/spark-network-yarn*.jar "$DISTDIR/lib/"
-cp "$FWDIR"/network/yarn/target/scala*/spark-network-shuffle*.jar "$DISTDIR/lib/"
-cp "$FWDIR"/network/yarn/target/scala*/spark-network-common*.jar "$DISTDIR/lib/"
 
 # Copy example sources (needed for python and SQL)
 mkdir -p "$DISTDIR/examples/src/main"