Improve assigned sync

Improve assigned tasks by handle Phabricator result and adding mappings for CI Robot

Phabricator API returns a object that does not always contain a dictionary, so improve the handling of empty results.

Also in order to assign tasks to CI Robot as a way to deal with test failures that are handled in a more specific task add a mapping for CI Robot.

Signed-off-by: Walter Lozano walter.lozano@collabora.com