Give a full path for glance verification

Give a specific directory so that it's clear that this is not a
subdirectory of the Image store (/var/lib/glance).

Also, remove the created directory at the end to make it clear that this
is a temporary download.

Change-Id: If42e5e891e728e7fb87318e29d88ede1376294b2
Closes-Bug: #1271018
Merge "Give a full path for glance verification"