Override /etc/network/interfaces in cleanup stage

Closes-Bug: #PROD-23196 (PROD:23196)
Change-Id: Ic0bf96afdf1b96f723d1fbde6cd4b751e7cc4077
diff --git a/common/ubuntu_cleanup.sh b/common/ubuntu_cleanup.sh
index 70b326b..13519ea 100644
--- a/common/ubuntu_cleanup.sh
+++ b/common/ubuntu_cleanup.sh
@@ -46,7 +46,7 @@
   echo > /var/log/cloud-init.log || true
 fi
 
-cat << EOF >> /etc/network/interfaces
+cat << EOF > /etc/network/interfaces
 # This file describes the network interfaces available on your system
 # and how to activate them. For more information, see interfaces(5).