TODO: There are still direct references to specific version of Python in:
  - slapos component
  - bazel templates
  - nextcloud & theia SR

@rafael says frontend infrastructure is not yet ready to handle slave
requests for frontends which come with lab.nexedi.com frontend SR URLs.

So revert apache-frontend-URL related part of 86deb9c6 (*: slapos.git
moved to https://lab.nexedi.com/nexedi/slapos.git) back for now.

/cc @jp
/reviewed-by @rafael
/reviewed-on nexedi/slapos!52

86deb9c6 (*: slapos.git moved to https://lab.nexedi.com/nexedi/slapos.git)
went over whole tree and updated slapos.git URL but when changing
non-top-software.cfg-like files forgot to update their md5sum in
software releases.

Fixes started to appear - e.g. 8b1496c3 (kvm: fix md5sum, thanks
@alain.takoudjou), but generally the whole tree remains more-or-less
broken.

Fix it. (not tested - manually checked files and updated md5sums)

/reported-by @rafael

no need to specify 'python = ${buildout:python}' because it is the default behaviour.