Nova evacuate failed when VM is in SHUTOFF status

When the VM is in SHUTOFF status and the original compute host is
down, issue the "nova evacuate" command to rebuild the VM on
another host, it is failed due to a type error: string indices
must be integers.

Fix bug 1176773
Change-Id: I76ebce6882198365717167f29a484e4ec994db0c
Merge "Nova evacuate failed when VM is in SHUTOFF status"