The ubuntu installer should delete old binaries

**Description**

The ubuntu installer (deb package) does not support special handling of "upgrade", i.e., when the node is already installed and a new version is being installed. In particular it does not delete the binaries of the old version. They are left in /usr/bin/ as zombies. They are unused by the upgraded package.

It would be better if the install script supported an "upgrade" as well and handled this appropriately.

The debian installer script is told already whether this is an upgrade or a fresh install, so it is possible to handle this.

Read the Debian installer script first, focusing on how it is told whether the package install is an upgrade or a fresh install. Reproduce an upgrade and inspect /usr/bin/ before and after it; done means binaries from the old version are removed rather than left as unused files.

Written by the indexing model from the issue text.