findmissing: missing: Convert to use logging facility

With logging now set up, let's use it.

BUG=None
TEST=Run on GCE

Change-Id: Ie13e416d1095b6cd35d432d25d6fef2d4155388f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2196522
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Commit-Queue: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
1 file changed