Our Windows build is failing currently because the couchbase server does
not handle a socket connection within a second (the default). This commit
adds a property to customize this option and set it to 10 sec in the
sample.

While investigating this issue, it turns out that while
`CouchbaseConfiguration` is public, it is not really possible to extend
it in user's configuration. This commit fixes this problem and add a test
that demonstrates how it can be used.

Closes gh-5657