[tracker] (6 commits) ...Merge branch 'wip/carlosg/test-error-fixes' into 'master'

[Sam Thursfield <sthursfield src gnome org>]

Summary of changes:

  69ee745... libtracker-data: Make get_db_interface() return a GError (*)
  247cdd2... libtracker-data: Propagate error on queries executed while  (*)
  f25c376... libtracker-sparql: Add early cancellation check on query ta (*)
  0f2b8b6... libtracker-data: Check for already visited properties durin (*)
  246d419... libtracker-data: Ensure to synchronize cached values after  (*)
  0ed35d1... Merge branch 'wip/carlosg/test-error-fixes' into 'master'

(*) This commit already existed in another branch; no separate mail sent