JCBC-327: Adding missing CouchbaseClientIF Signatures.

Change-Id: I505b95d1dbc76a365572ded83c85c5e6581ffe3e
Reviewed-on: http://review.couchbase.org/27307
Reviewed-by: Deepti Dawar <deepti.dawar@globallogic.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>