For k8s, use provisioner-managed volumes when an absolute host path is not specified. (#741)

In kind, when we bind-mount a host directory it is first mounted into the kind container at /mnt, then into the pod at the desired location.

We accidentally picked this up for full-blown k8s, and were creating volumes at /mnt.  This changes the behavior for both kind and regular k8s so that bind mounts are only allowed if a fully-qualified path is specified.  If no path is specified at all, a default storageClass is assumed to be present, and the volume managed by a provisioner.

Eg, for kind, the default provisioner is: https://github.com/rancher/local-path-provisioner

```
stack: test
deploy-to: k8s-kind
config:
  test-variable-1: test-value-1
network:
  ports:
    test:
     - '80'
volumes:
  # this will be bind-mounted to a host-path
  test-data-bind: /srv/data
  # this will be managed by the k8s node
  test-data-auto:
configmaps:
  test-config: ./configmap/test-config
```

Reviewed-on: cerc-io/stack-orchestrator#741
Co-authored-by: Thomas E Lackey <telackey@bozemanpass.com>
Co-committed-by: Thomas E Lackey <telackey@bozemanpass.com>

stack_orchestrator/data/compose/docker-compose-test.yml

@@ -7,11 +7,13 @@ services:
       CERC_TEST_PARAM_1: ${CERC_TEST_PARAM_1:-FAILED}
       CERC_TEST_PARAM_2: "CERC_TEST_PARAM_2_VALUE"
     volumes:
-      - test-data:/data
+      - test-data-bind:/data
+      - test-data-auto:/data2
       - test-config:/config:ro
     ports:
       - "80"
 
 volumes:
-  test-data:
+  test-data-bind:
+  test-data-auto:
   test-config: