update assertions in tests

Add the following entries to the expectation of assertions:

1. "headers"; introduced in adadd2d (Added HTTP Request headers)

2. "rejectUnauthorized"; introduced in 3de6efa (Pass
   rejectUnauthorized option to Node http.request)
tests: DRY up default entries in assertion expectations

This way, new entries added to the return values of najax() in the
future can be added in one place easily.
tests: mention port 443 in description of ssl assertions