[tracker] (8 commits) ...Merge branch 'prevent_saving_half_completed_db' into 'master'

[Sam Thursfield <sthursfield src gnome org>]

Summary of changes:

  ed65749... tracker-db-manager: add "first_time" field
  255123a... delete the half-completed db if the db creation failed
  2b98327... propagate errors that happen while updating an existing db 
  1f3416d... update ontology last modified field inside the ontology tra
  53fba64... add a test case for ontology rollback on failure
  4b715bb... ontology-changes.py: prevent some tests from being skipped
  08e55cc... ontolog-changes.py: mark some tests as expected failure
  eea3220... Merge branch 'prevent_saving_half_completed_db' into 'maste