KEY_NOT_FOUND with max keylen and chunksize=16

added a test that does set/get of a key with FDB_MAX_KEYLEN:
http://review.couchbase.org/51581

the set passes but get fails
308 // set kv
309 status = fdb_set_kv(db, keybuf, strlen(keybuf), NULL, 0);
310 TEST_CHK(status == FDB_RESULT_SUCCESS);
311
312 // get kv
313 status = fdb_get_kv(db, keybuf, strlen(keybuf), &rvalue, &rvalue_len);
314 TEST_CHK(status == FDB_RESULT_SUCCESS);
(lldb) print status
(fdb_status) $1 = FDB_RESULT_KEY_NOT_FOUND
(lldb)