Revert "Use lazy umount to unmount loopback devices."

This reverts CL:191524. This CL is suspected of breaking all
paladin builders, and some of the canaries.

BUG=chromium:353558
TEST=none

Change-Id: Ie1d692cde38c1183cb0e2e776e2785458f68d0e8
Reviewed-on: https://chromium-review.googlesource.com/191615
Reviewed-by: David James <davidjames@chromium.org>
Tested-by: David James <davidjames@chromium.org>
1 file changed