PYCBC-91: Test for UTF-16 keys

Change-Id: Ia64bc36ae13f6769dec5031eaae156625f754c8b
Reviewed-on: http://review.couchbase.org/25937
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Matt Ingenthron <matt@couchbase.com>