Update weave to 2.8.1 and manifest to address CVE-2020-26278

[mmerrill3]

1. What kops version are you running? The command kops version, will display
this information.
kops 1.19.beta3
2. What Kubernetes version are you running? kubectl version will print the
version if a cluster is running or provide the Kubernetes version specified as
a kops flag.
k8s 1.19.6
3. What cloud provider are you using?
aws
4. What commands did you run? What is the simplest way to reproduce this issue?
n/a
5. What happened after the commands executed?
n/a
6. What did you expect to happen?
n/a
7. Please provide your cluster manifest. Execute
kops get --name my.example.com -o yaml to display your cluster manifest.
You may want to remove your cluster name and other sensitive information.

8. Please run the commands with most verbose logging by adding the -v 10 flag.
Paste the logs into this report, or in a gist and provide the gist link here.

9. Anything else do we need to know?

Weave has moved the hostPID:true ability to an init container, mitigating a security vulnerability. This requires weave 2.8.1, and an update to the manifest for the weave daemon set.