Provide a means of setting vmdk custom properties via image filename

Custom properties for vmdk disk type, storage adapter type, and
networking adapter type can now be retrieved from a vmdk image's
filename. The filename format is defined as:

  <name>-<disk type>:<storage adapter>:<network adapter>

An example filename following this format would be
debian-2.6.32-i646-thin:ide:VirtualE1000. If the vmdk filename does not
match the above format then underlying nova driver will supply default
values.

Change-Id: I83483d20f984250bd8154d8e270b2e801d2df303
Closes-bug: #1221044
Merge "Provide a means of setting vmdk custom properties via image filename"