Updated options parser to ignore values set to `undefined`.

Change-Id: Iade6c06b50644e90139dc8a8e89c4594d36014d5
Reviewed-on: http://review.couchbase.org/30824
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Brett Lawson <brett19@gmail.com>