When adding the ephemeral volume feature, the special case for
PersistentVolumeClaim volume sources in kubelet's host path and node
limits checks was overlooked. An ephemeral volume source is another
way of referencing a claim and has to be treated the same way.
Some plugins expect the new feature gate struct. We can inject that additional
parameter via a helper function instead of having to repeat the same anonymous
function for each plugin.
Check the PVC ref count on the node info cache to determine if a pod's
PVCs are in use. If they are and it is using ReadWriteOncePod, fail the
request.
kubernetes#60525 introduced
Balanced attached node volumes feature gate to include volume
count for prioritizing nodes. The reason for introducing this
flag was its usefulness in Red Hat OpenShift Online environment
which is not being used any more. So, removing the flag
as it helps in maintainability of the scheduler code base
as mentioned at kubernetes#101489 (comment)
