restore: use unique temporary tar filename
restore: use unique temporary tar filename

Also remove the tar file after we're done with it to prevent it from being
bundled into new basebackups that are created from the pgdata we downloaded
it to.

hnousiainen/pghoard,ohmu/pghoard,saaros/pghoard,Ormod/pghoard,hnousiainen/pghoard,ohmu/pghoard,melor/pghoard,kri5/pghoard