Mounting a pvc in a single pod builder multiple times, results in conflicts

[roderik]

Steps to reproduce

1. create a pvc like in the examples
2. create a podbuilder with 2 init containers and 1 normal container
3. all these containers will interact with the data on the pvc so they all have volumeMounts: [ pvc.mount('/data')]
4. the volumes in the spec builder is not a set, but an array, so it will have 3 volumes for the same pvc
5. error

Went to a manual Deployment in the end.

[lukehoban]

Sounds like we'll need to do a set union of the volumes instead of just concatenating them. PRs definitely welcome!