Only copy symlink name of logs

devstack creates a shortened symlink without timestamp (foo.log ->
foo.2014-01-01-000000.log) for each log to latest log. Thus we just
copy the symlinks to avoid excessively long file-names.

This removes the need to remove duplicate log files, which was
incorrectly removing grenade.sh.log (because it has multiple '.'s and
kind of looks like the time-stampped log files)

The grenade log cleanup is added in a separate section.  In general,
it should be better to clean-up logs in a more specific fashion like
this to avoid the situtation where a glob match removes things we
really want.

Also, there is no $BASE/new/devstacklog.txt.  The devstack upgrade
process is driven by grenade.sh which calls parts of devstack
directly; so all relevant log output goes into grenade.sh.log

Change-Id: Ib1c4476c28c5c032ed9ab1682118a4f4528db450
Merge "Only copy symlink name of logs"