GREEN-1938: Use the ffi-napi modules in tests (#30)

Some of the unit tests were requiring the ffi modules to test the ability
to extend the API. Since we updated package.json to use the ffi-napi module,
the ffi module is no longer present and these tests were failing.

Co-authored-by: Sam Raeburn <sam@rti.com>

Author: samuelraeburn

test/nodejs/test_rticonnextdds_data_access.js

@@ -8,7 +8,7 @@
 
 const path = require('path')
 const os = require('os')
-const ffi = require('ffi')
+const ffi = require('ffi-napi')
 const chai = require('chai')
 const chaiAsPromised = require('chai-as-promised')
 const expect = chai.expect

test/nodejs/test_rticonnextdds_input.js

@@ -8,7 +8,7 @@
 
 const path = require('path')
 const os = require('os')
-const ffi = require('ffi')
+const ffi = require('ffi-napi')
 const chai = require('chai')
 const chaiAsPromised = require('chai-as-promised')
 const expect = chai.expect