Update for OpenCI migration

- Upgrade packer as it is way too old to support IAM based authentication
- Add VPC_ID and SUBNET_ID in environment variables to support multiple
  infrastructure like DEV, TEST, PROD etc
- Add "packer_" tags to identify instances spun up by packer.
- Increase node size as Docker images are getting bigger

Change-Id: I10bb88affd9f408dc40ae0041adef647077ff7a3
Signed-off-by: Saheer Babu <saheer.babu@arm.com>
diff --git a/custom.sh b/custom.sh
index 0927cab..7d13ada 100755
--- a/custom.sh
+++ b/custom.sh
@@ -51,8 +51,7 @@
 
 sed -i -e 's/#PermitTTY.*/PermitTTY yes/g' /etc/ssh/sshd_config
  
-# install packer.  We are using an older version because current 1.8.5 has
-# a bug in it that prevents the temp ssh key from being setup for freebsd
-curl --output packer.zip https://releases.hashicorp.com/packer/1.5.1/packer_1.5.1_linux_amd64.zip  
+curl --output packer.zip https://releases.hashicorp.com/packer/1.11.2/packer_1.11.2_linux_amd64.zip
 unzip -o packer.zip
 install -m 755 packer /usr/bin/packer
+packer plugins install github.com/hashicorp/amazon 1.3.3