Clean up failed image transfers in instance spawn

Boot one instance with powervm driver, will transfer the image
file to host. Need clean up failed image transfers that may occur
during instance spawn.

Fixes bug #1173017
(cherry picked from commit 68cc1cd511298208dde59878bfbef474a3625c9f)

Change-Id: Id06fa84bee63adc4af96a339526d75540978263f
Merge "Clean up failed image transfers in instance spawn" into stable/grizzly