The 'local_software_release_root' parameter can be set in slapos.cfg:
    [slapproxy]
    local_software_release_root = <path>
or via the command line using:
    slapos proxy start --local-software-release-root <path>

When slapproxy starts, it updates all local URLs that are subpaths of
the previous root path to be subpaths of the new root path instead:
    <previous-root-path>/<subpath>   =>   <new-root-path>/<subpath>

The default root path is '/'. This means that by default slapproxy
behaves the same as before.