cluster-launch-installer-e2e: Set expirationDate tags

For four hours in the future.  Successful runs are currently taking
around 40 minutes [1], so this gives us a reasonable buffer without
leaving leaked resources around forever.

[1]: https://deck-ci.svc.ci.openshift.org/?job=pull-ci-origin-installer-e2e-aws&state=success

Author: wking

cluster/ci/config/prow/jobs/cluster-launch-installer-e2e.yaml

@@ -191,6 +191,7 @@ objects:
           export EMAIL=test@ci.openshift.io
           export PASSWORD=$( date +%s | sha256sum | base64 | head -c 32 ; echo )
           export EC2_AMI_OVERRIDE=ami-02323e873420d8eab
+          export EXPIRATION_DATE=$( date -d '4 hours' --iso=minutes --utc )
           cat /etc/openshift-installer/openshift.yaml | envsubst > /tmp/cluster/inputs.yaml
         )
         echo "Invoking installer ..."

cluster/test-deploy/aws/openshift.yaml

@@ -73,7 +73,7 @@ aws:
   # (optional) Extra AWS tags to be applied to created resources.
   #
   # Example: `{ "key" = "value", "foo" = "bar" }`
-  # extraTags:
+  extraTags: {"expirationDate" = "${EXPIRATION_DATE}"}
 
   # (optional) Name of IAM role to use to access AWS in order to deploy the Tectonic Cluster.
   # The name is also the full role's ARN.