Fix edge cases around device lists (#1234)

* Fix New users appear in /keys/changes

* Create blank device keys when logging in on a new device

* Add PerformDeviceUpdate and fix a few bugs

- Correct device deletion query on sqlite
- Return no keys on /keys/query rather than an empty key

* Unbreak sqlite properly

* Use a real DB for currentstateserver integration tests

* Race fix

keyserver/internal/internal.go

@@ -206,6 +206,9 @@ func (a *KeyInternalAPI) QueryKeys(ctx context.Context, req *api.QueryKeysReques
 				res.DeviceKeys[userID] = make(map[string]json.RawMessage)
 			}
 			for _, dk := range deviceKeys {
+				if len(dk.KeyJSON) == 0 {
+					continue // don't include blank keys
+				}
 				// inject display name if known
 				dk.KeyJSON, _ = sjson.SetBytes(dk.KeyJSON, "unsigned", struct {
 					DisplayName string `json:"device_display_name,omitempty"`