VMware: fix disk extend bug when no space on datastore

In the event that thete is no space on the datastore then ensure
that the disk extension is cleaned up accordingly.

A number of files would be left behind on the datastore.

Change-Id: Ica9daf9151e4fb1874fa8b1d7247080860ef4ae2
Related-Bug: #1255355
(cherry picked from commit 787d36b40b41c1ee1e56ae3f8d17984e70c59a8e)