Improve error message for failed CDI loads

[balazsracz]

Currently when the CDI.xml loading fails, the user gets an error like this:

This is not super helpful to the user. We should record what the underlying problem was, and give the actual error to the user.
e.g. in thew above case the node was not replying to the READ commands (datagram timeout), but the entire node was completely unreachable.