cros_generate_update_payload: Add retries to umount operations.

Add retries around umount operations that have been failing
under heavy load. Add additional logging of system stats
before each retry.

BUG=chromium:353558
TEST=cros flash to local dev box.

Change-Id: Id23cd5cc50ff0d216122e42e0356f1d1b61e1c8b
Reviewed-on: https://chromium-review.googlesource.com/191365
Reviewed-by: David James <davidjames@chromium.org>
Commit-Queue: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
1 file changed