Remove stale log files and speed up apache log sync

* Major speedup: The apache log directory was pointlessly being copied
  for each user on each sync so that it could be chowned and
  transferred. But there is no need: afs ignores the owner/group and
  unix permissions and root can read the keytabs. Eliminating the
  redundant copy sped the script by from ~9 minutes to ~2 minutes.
* Limit scope of each transfer to the per-host apache log
  directory. This could result in less stat()ing, but more importantly
  allows us to...
* Pass --delete to rsync to clean up stale log files. It turns out
  that for a very long time we've just been leaving the uncompressed
  logrotated apache logs behind, and never removing old log files. Fix
  that.