Fix V3 API server extension point exception propagation

Adds the propagate_map_exception parameter to extension
manager initialisation in the servers plugin so extension
points for the V3 API propagate exceptions rather than
supress them. The parameter was missing from some of the
extension point managers.

Also adds a missing V3 API personality test which exposed
the problem with exceptions not being correctly propagated.

Very minor spelling fix to one of the tests

Change-Id: I53fa680cfab9219442610a5dceeb35b150314f6f
Closes-Bug: 1224293
Don't fail if volume has no image metadata

In the same way that nova shouldn't fail when booting an instance if the
image has no metadata, when booting from a volume it should accept the
fact that it has no image_metadata and return an empty dict.

Fixes bug #1220814

Change-Id: Idc0ff2106415a0662e57021e918dc5c6bf9a9a92
Merge "Fix V3 API server extension point exception propagation"
Merge "Don't fail if volume has no image metadata"