The configuration `dcache-view.endpoints.webdav` should always be enforced

[paulmillar]

The configuration property dcache-view.endpoints.webdav (in dCache as frontend.static!dcache-view.endpoints.webdav) is used as a fallback.

This property, if set, should override any auto-discovery mechanism.

In addition, it doesn't always work (see #250). It should also work.