Fetch from branch v4 in Spark EC2 script.

ec2/spark_ec2.py

@@ -583,7 +583,7 @@ def setup_cluster(conn, master_nodes, slave_nodes, opts, deploy_ssh_key):
 
     # NOTE: We should clone the repository before running deploy_files to
     # prevent ec2-variables.sh from being overwritten
-    ssh(master, opts, "rm -rf spark-ec2 && git clone https://github.com/mesos/spark-ec2.git -b v3")
+    ssh(master, opts, "rm -rf spark-ec2 && git clone https://github.com/mesos/spark-ec2.git -b v4")
 
     print "Deploying files to master..."
     deploy_files(conn, "deploy.generic", opts, master_nodes, slave_nodes, modules)