Make DeferredUpdates able to run DataUpdates

Make DeferredUpdates able to run DataUpdates

* Also make ErrorPageError exceptions display themselves
  in PRESEND mode. Before they were always suppressed.
* Make DataUpdate::runUpdates() simply wrap
  DeferredUpdates::execute().
* Remove unused installDBListener() method, which was
  basically moved to Maintenance.
* Enable DBO_TRX for DeferredUpdates::execute() in CLI mode
* Also perform sub-DeferrableUpdate jobs right after their
  parent for better transaction locality.
* Made rollbackMasterChangesAndLog() clear all master
  transactions/rounds, even if there are no changes yet.
  This keeps the state cleaner for continuing.
* For sanity, avoid calling acquirePageLock() in link updates
  unless the transaction ticket is set. These locks are
  already redundant and weaker in range than the locks the
  Job classes that run them get. This helps guard against
  DBTransactionError.
* Renamed $type to $stage to be more clear about the order.

Change-Id: I1e90b56cc80041d70fb9158ac4f027285ad0f2c9