CCBC-924: initialize flag for JSON server feature
CCBC-924: initialize flag for JSON server feature

Otherwise it might be left uninitialized and the library will
send JSON datatype to servers, which do not support it.

Change-Id: Ib316816d1db4a7071a4864c7293f4ad374b01eac
Reviewed-on: http://review.couchbase.org/93641
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Pavel Paulau <dd88eded64e90046a680e3a6c0828ceb8fe8a0e7@gmail.com>
Tested-by: Pavel Paulau <dd88eded64e90046a680e3a6c0828ceb8fe8a0e7@gmail.com>

couchbase/libcouchbase,avsej/libcouchbase,avsej/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase,kojiromike/libcouchbase,avsej/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,kojiromike/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,avsej/libcouchbase