Bug 1070487 - [keyboard] unit test refactoring for new version chai.assert api

test_agent used very old version chai library version=0.5.3
in the current version=1.9.1 same api chenged 

1. assert.length -> assert.lengthOf
2. in new version assert.deepEqual take prototype into consideration same test need change

this compatible with both old and new version chaijs library
Please help update the above comment to reflect the updated fact.