Don't wrap Glance exceptions in NovaExceptions

Exception objects from glanceclient are not serializable
in Nova and shouldn't be directly wrapped inside NovaExceptions.
The glanceclient portions of Nova that translate from Glance
to Nova should be creating new corresponding exceptions
independent of the Glance counterparts.

Change-Id: Ifbe992796f8c5738ae350617d41a9c312fa8ab94
Merge "Don't wrap Glance exceptions in NovaExceptions"