Replace K8s 1.21.3 with 1.21.8

In testing K8s 1.21.8 used less CPU than 1.21.3, so we are moving to
the newer version.

This has been booted in vbox and a basic pod has been started.
A full regression will be performed.
Still need to install with 1.20 to confirm that we can upgrade to
1.21.8.

Closes-Bug: 1957994
Depends-On: https://review.opendev.org/c/starlingx/integ/+/824803
Depends-On: https://review.opendev.org/c/starlingx/ansible-playbooks/+/824805
Signed-off-by: Chris Friesen <chris.friesen@windriver.com>
Change-Id: I7c6a75ff9bbdddf1bfab3d2ea71a25224293d989

sysinv/sysinv/sysinv/sysinv/common/kubernetes.py

@@ -147,7 +147,7 @@ def get_kube_versions():
          'applied_patches': [],
          'available_patches': [],
          },
-        {'version': 'v1.21.3',
+        {'version': 'v1.21.8',
          'upgrade_from': ['v1.20.9'],
          'downgrade_to': [],
          'applied_patches': [],