Prevent OqJob and Hazard/Risk Calculation reference key inconsistencies

[matley]

We need to prevent the situation where a calculation (Hazard/Risk) is saved without the corresponding job. E.g.

openquake --lhc i get:

calc_id | status | last_update | description
1 | successful | 2013-09-18 11:15:02 | Disaggregation calculation for Portugal with AB2010
2 | successful | 2013-09-18 13:53:21 | Disaggregation calculation for Portugal with Ba2006
4 | pending | 2013-09-18 17:15:22 | Disaggregation calculation for Portugal with bothGMPE
Traceback (most recent call last):
  File "/usr/local/openquake/oq-engine/bin/openquake", line 512, in <module>
    main()
  File "/usr/local/openquake/oq-engine/bin/openquake", line 459, in main
    list_hazard_calculations()
  File "/usr/local/openquake/oq-engine/bin/openquake", line 293, in list_hazard_calculations
    _print_calcs_summary(hcs)
  File "/usr/local/openquake/oq-engine/bin/openquake", line 316, in _print_calcs_summary
    latest_job = calc.oqjob
  File "/usr/lib/python2.7/dist-packages/django/db/models/fields/related.py", line 257, in __get__
    rel_obj = self.related.model._base_manager.using(db).get(**params)
  File "/usr/lib/python2.7/dist-packages/django/db/models/query.py", line 365, in get
    % self.model._meta.object_name)
openquake.engine.db.models.DoesNotExist: OqJob matching query does not exist.

[Daniele Viganò (daniele-vigano)]

Original bug report https://bugs.launchpad.net/oq-engine/+bug/1227472

[matley (matley)]

This happens also when an user uses the import facilities, e.g.:

openquake --load-curve curve.xml

Then, openquake --lhc fails

[matley (matley)]

https://github.com/gem/oq-engine/pull/1281