Move full-stack logs post-tests

Move full-stack logs post-tests

Currently, it's up to the developer who wants to run full-stack on his
machine to make the directory in question (/opt/stack/logs). However,
this also means that the files don't get compressed at the end of a gate
run. Now, each full-stack test will have each own log directory in /tmp.
Once the logs are there, post_test_hook.sh can run 'gzip' on all the log
files before moving them to /opt/stack/logs on its own.

Change-Id: I5c04d0af0b9858722ae0c4baf0ee478ffb078e02