portsnap: use lam on the 'good' hash list instead of sed on the untrusted one

[emaste]

Summary

This change should be equivalent to the approach committed in rS306417, but if sed has a bug it could be exploited by the untrusted tar file. Instead, convert the expected hash list to the expected tar content filesystem layout, and compare that with find's output.

Submitted by: @cperciva in D8052

[allanjude]

I am capsicumizing lam(1), and will have a review soon

[oshogbo]

usr.sbin/portsnap/portsnap/portsnap.sh

694

\ - is not needed, or you should add some space like in rest file.

[emaste]

Committed in rS306825