Let key-less PCs ask to enroll, and let an admin retry a trust-blocked PC

Found in the Windows VM re-test.

- A PC installed without the shared key got 401 from POST
  /api/endpoints/enroll while the shared key was allowed, so no request was
  recorded and no admin could approve it. Enroll now never refuses: a valid
  shared key only decides auto-issue on a clean match; no key or an invalid
  key creates or updates the one pending request for that hostname and
  serial. An approved request still issues only to its own nonce.
- A PC blocked with "server certificate not trusted by this PC" could never be
  queued again after trust was fixed, because the blocker comes from its last
  failed upgrade. Naming the PC in a wave now queues it when trust is its only
  blocker, and the response lists it under "retried"; "next n" still skips
  it. The Migration table lets such a PC be selected.
- counts.pending on GET /enrollment counts pending requests, including ones
  for unknown hostnames; counts.pendingcomputers keeps the per-computer figure.

plugins/endpoints/frontend/views/agentKeySettings.spec.js

@@ -23,7 +23,7 @@ function enrollmentPayload(settings = { sharedkeyallowed: true, autoenroll: true
     data: {
       data: {
         settings,
-        counts: { enrolled: 30, notenrolled: 8, pending: 2 },
+        counts: { enrolled: 30, notenrolled: 8, pendingcomputers: 2, pending: 3 },
         computers: [],
         requests: [
           { requestid: 1, status: 'pending', reason: 'serial mismatch' },