milton-client: Preemptive digest auth is broken

[almson]

The PreemptiveAuthInterceptor doesn't work correctly because it is insert at the beginning, before authState.getAuthScheme() is set by another intercepter. One solution seems to set it at both the beginning and the end.

Host.java:236

    client.addRequestInterceptor(interceptor, 0);

should be

    client.addRequestInterceptor(interceptor, 0);
    client.addRequestInterceptor(interceptor);

[ophiuhus]

Hey @almson. Thanks, we will take a look.