Used unique temp dirs when mounting images.
Used unique temp dirs when mounting images.

Multiple copies of the function verify_image should now be able to run without
interfering with each other.

BUG=none
TEST=./image_to_live.sh ... worked.

Change-Id: I76f252ec0981ed00faaf2ff90ee41e6b19c5a372
Reviewed-on: http://gerrit.chromium.org/gerrit/6620
Tested-by: asharif <0bffdc695497b480334d6a40467f7e340b20eba1@chromium.org>
Reviewed-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>

marineam/coreos-dev-util,marineam/coreos-dev-util,mgireesh05/dev-util,coreos/dev-util,coreos/dev-util,mgireesh05/dev-util,mgireesh05/dev-util,coreos/dev-util