bin/124915: bsdtar(1) creates files with bogus access times

[Tim Kientzle]

Ouch.  Yep, plain tar format doesn't store an atime,
so the atime value for the entry gets extracted as zero
and the archive_extract() routine ends up restoring
the file atime as zero.

There's a couple of ways this might be fixed.  I'm
not sure offhand whether it's better to explicitly
set the atime to match mtime or to the current time.