Bug 1090043 - [B2G][Message] MMS attachments missed in SMIL could not be displayed

- Check if the attachment count match the SMIL and force to parse without SMIL if the count is unmatched
- Make sure mimetype 'application/***' is visible in thread (parseWithoutSMIL case) 
nit: use the form `done(function() {
  // assertions
});
`
so that errors are correctly caught