Disable default volumes in podTemplate overrides

[sebgl]

Forked from the Beat CRD PR (#3041 (comment)).
I don't think we have a way for the user to override a volume so it isn't appended by default. Which may be useful for metricbeat or filebeat, if you don't want to mount /proc or /var/log/containers for example.

[david-kow]

As user podTemplate is applied first and not overwritten I think the below should work (not tested though):

volumes:
- name: proc
  emptyDir: {}

Seems hacky, so some alternatives:

1. flag to prevent adding default volumes
2. list field of default volume names to exclude
3. don't use default volumes if the user provides a config

[david-kow]

As we decided to go with no defaults approach, this is no longer an issue. Closing.