Use tmpdir within /data for barman-cloud-backup/-restore

[immerrr]

We are having an issue with postgres backups created by barman: they are failing, because barman creates a tar archive in /tmp directory, which only has ~7.5G to work with, so it runs out of space.

# df -h
Filesystem      Size  Used Avail Use% Mounted on
none            7.8G   48M  7.4G   1% /
/dev/vdb        7.8G   48M  7.4G   1% /.fly-upper-layer
shm             2.0G  3.1M  2.0G   1% /dev/shm
tmpfs           2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/vdc        147G   20G  121G  14% /data

I've checked barman sources, and it didn't seem to have a way to configure its temp. directories, so I ended up making a wrapper script that creates a temporary directory in a place of your choice, and configured barman-cloud-backup and barman-cloud-restore commands to run through that script.

There should be a better way to handle this, but I wanted to get some early opinions on this.

Also, had to fix the haproxy configs, it seemed to complain about having two server-template clauses with the same name pg