Fix break in vm_vdi_cleaner after oslo changes.

Added missing imports along with adding a call to config.parser_args as needed
to allow vm_vdi_cleaner to work against current master.

Corrected spelling error in comment.

Change-Id: I4d30d0f7f9718cb29fb8c4c18e9e6fa23f3496ef
Closes-Bug: #1279942
Merge "Fix break in vm_vdi_cleaner after oslo changes."