ZP-848 SetSyncKey in SPO always if it is set (as before), but invalidate

FolderStat if it does not change.

Released under the Affero GNU General Public License (AGPL) version 3.

src/lib/request/sync.php

@@ -164,9 +164,11 @@ class Sync extends RequestProcessor {
                             $spa->RemoveSyncKey();
                             $spa->DelFolderStat();
                         }
-                        else if ($synckey !== false && $synckey !== $spa->GetSyncKey()) {
+                        else if ($synckey !== false) {
+                            if ($synckey !== $spa->GetSyncKey()) {
                                 ZLog::Write(LOGLEVEL_DEBUG, "HandleSync(): Synckey does not match latest saved for this folder, removing folderstat to force Exporter setup");
                                 $spa->DelFolderStat();
+                            }
                             $spa->SetSyncKey($synckey);
                         }
                     }