astakosclient: Use 'repr' when logging

Use 'repr' instead of 'str' when logging the response body.
astakosclient: Human readable details message

In case of QuotaLimit exception, fill 'details' with a human readable
message and put the actual JSON response in the 'response' variable.
Synnefo UI shows the 'details' field of an exception to the user so it
has to be human readable.
astakosclient: Fallback to json module

If 'simplejson' module is not available fallback to 'json'.
cyclades: Update snapshot based on Ganeti job

Make Cyclades update the state of a snapshot in Pithos DB based on
the result of the corresponding Ganeti job. This is required to be
performed by Cyclades, because Pithos has no way to know whether an
unavailable snapshot will ever by completed or not (e.g. the Ganeti
job failed or it still has not completed).

Refs grnet/synnefo#231
cyclades: Reconciliation for stale snapshots

Extend 'reconcile-servers' command to perform reconciliation for
snapshots, which can occur if the Ganeti job failed but the
corresponding message from eventd has never been processed. In order to
make reconciliation possible, Cyclades store a special metadata on the
snapshot that contains the Ganeti ID and the job ID that will create the
snapshot.

Closes grnet/synnefo#231
cyclades: Fix PEP8 issues