locksettings: zero-pad IDs when shown as hex

When printing a 'long' ID as hex, use %016x instead of %x so that the
width is always consistent, not shorter 1/16 of the time.  This also
matches the way the synthetic password state files are named.

Bug: 268526331
Change-Id: I999606ff0d6a19641f32c4f4826476b4a839ad59