This may happen if the initial cache sync takes longer than the
monitor interval.

Take no action for a deleted ConfigMap, other than resetting current
knowledge of VCL mtimes.

This is a key in the ConfigMap used for VCL configuration. If set,
and if the value is not empty, then the value is a version string
for the VCL config. It is used in the generation of the VCL config
name, and in the fqVersion function for VCL templates.

Eliminates a warning message at startup.

After vcl_cooldown, VCLs since Varnish at least 6.3 go to cold
temperature, but stay in the auto state.

Cold state happens when a VCL is set to cold via vcl.state, in which
case the temperature also goes cold. So an admin might hasten the
discard by setting the cold state.

It should be configurable whether this happens -- an admin may want
to intentionally stop Varnish, and this feature would interfere with
that.

Get some mod tidy done while we're here.

In case Pod names ever change without changing endpoint addresses.

We don't need a binary-to-text encoding for the hash, we just test
the binary result. We also don't need to sort []Endpoint or hash
Service.

InitTemplates() takes a map of template paths to file paths, and
returns a map of parsed template to file paths.

Add WriteTemplate(), which takes a parsed template and a file path,
and generates VCL at the path from a spec and the template. Meant
for iteration on the map returned by InitTemplates().