cyclades: Fix bug during server creation
Commit #32a0b85, modified server creation, by refetching the object from DB after issuing commission to quotaholder. However, the new object is not having the 'config_url' attributed, which is added to the vm object by the 'vmapi'. This commit, fixes this by moving the signal dispatching code after refetching the vm. Also, this commit makes more clear the exception handling code, when the creation job can not be enqueued to Ganeti.