Add mop lifecycle hooks

[jackfrancis]

No description provided.

[jackfrancis]

So far I've confirmed that using container lifecycle hooks doesn't do what we want:

      containers:
        - name: {{ .Values.mop.name }}
          lifecycle:
            preStop:
              exec:
                command:
                  - sh
                  - -c
                  - >-
                    if ! test -f /var/maintenance-in-progress; then
                      rm -f /var/maintenance-required;
                      rm -f /var/{{.Values.mop.priority}}.validation-required
                    fi;

For reference see:

• https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/

I also experimented a bit with Helm Chart Hooks (post-delete) and couldn't get that to work either, but that may be the path forward. See:

• https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/