Client does not return the correct exit code when failing to communicate with server.

[Chris Glass]

As part of the fallout from recent changes in the client configuration, the trunk client does not exit the same way as before.

One error, the previous client did and "exit(2)" (and exit(1) should the configuration file be unreadable)

We should at least reinstate the exit(2) behavior since robot tests rely on it and it is a reasonable assumption that a program returns a non-zero exit code on failure.