VMware: uncaught exception during snapshot deletion

During the image upload of the snapshot to glance, an exception is
thrown that ends up getting ignored.  As a result, the instance gets
stuck in the "Image Uploading" state.

Change-Id: Id2cb3c244edd831939794da9dcc1fd9fce59991c
Closes-bug: #1249519
(cherry picked from commit 56607f9af4495e76edf6675a984a66da907c89f8)
Merge "VMware: uncaught exception during snapshot deletion" into stable/icehouse