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
Merge "VMware: fix disk extend bug when no space on datastore"