Force 1.6 Java Compat even with 1.7 and up.

Change-Id: I968446387a0fb9b9edf69ddce9e79da21f5fa153
Reviewed-on: http://review.couchbase.org/26150
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Deepti Dawar <deepti.dawar@globallogic.com>