Converting deprecated methods on channelbuffer.toString()

Change-Id: Ia4e2d9e11cba976f7aa230029b32bd303bc98df1
Reviewed-on: http://review.couchbase.org/30374
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>