Install openvswitch even with --cord prerequisites option as it doesn't seem to be installed on cord head node

Change-Id: I95ba4803ecf0b38423c07cad98d7365991abab03
diff --git a/src/test/setup/prerequisites.sh b/src/test/setup/prerequisites.sh
index d79b963..3691198 100755
--- a/src/test/setup/prerequisites.sh
+++ b/src/test/setup/prerequisites.sh
@@ -24,8 +24,8 @@
     docker rmi hello-world
     echo "Pulling ONOS latest"
     docker pull onosproject/onos:latest || exit 127
-    apt-get -y install openvswitch-common openvswitch-switch
 fi
+apt-get -y install openvswitch-common openvswitch-switch
 apt-get -y install wget git python python-dev python-pip python-setuptools python-scapy python-pexpect python-maas-client tcpdump arping libssl-dev
 easy_install nose
 pip install scapy==2.3.2