Invoice View: Fix conditions that stop invoice reload

* Previously isPaid immediately stopped the reload loop.
  This is problematic because a paid invoice that becomes unpaid due to a
  double spend would fail to reload and inform the user of that fact.
  This was fixed by stopping the reload loop when isPaid && !watchingAnyPayment().
* Previously isVoid and isExpired failed to set the page properties informing
  the user about the status.
* Previously onload invoice would display expiration countdown for 15 seconds
  before showing the Void or Expired status.  Fixed in both invoice.ejs and
  by starting the expirationUpdateJob only after the first requestInvoice().