deploy: Do not run archipelago as root

Since 0.4~rc2, archipelago creates archipelago user and group
upon package installation. In order not to run as root we
have to:

 - chown and chmod /srv/archip dirs and file
 - let gunicorn run as www-data.archipelago
 - chown /etc/synnefo and /var/log/gunicorn

Additionally archipelago introduces an new dir to store locks.
Create this dir on the nfs node.

NOTE: In case of a multinode setup using NFS as archipelago
backend, the archipelago user must have a common group id across
all nodes. Currently snf-deploy does not take that into account
since it practically setups a single node installation.

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
deploy: Remove pithos_dir references

Since archipelago is the pithos backend, the NFS dir /srv/pithos
is useless. Cleanup everything related to it.

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>