ocdav service still using machine auth

[kobergj]

The ocdav service (living in reva) is still using machine auth in some cases. We want to use service accounts instead

Acceptance criteria:

• [ ] pass service account config to ocdav
• [ ] find occurences of machine auth (search for MachineAuthAPIKey) and replace them with service accounts
• [ ] remove MachineAuthAPIKey config var in ocdav (reva)

[kobergj]

Two occurrences of this in revas ocdav service: https://github.com/cs3org/reva/blob/edge/internal/http/services/owncloud/ocdav/ocdav.go#L343 https://github.com/cs3org/reva/blob/edge/internal/http/services/owncloud/ocdav/ocdav.go#L370