Revert "increase slapos.libnetworkcache version, because slapos.recipe.build needs a recent version"

This reverts commit 51fb8ca1.

This reverts commit 91168c43.

This reverts commit 5bde992d.

This rever commits
2def7c36
92302152

This reverts commit fdb2b87b.
This breaks erp5 test runner (maybe it does not accept IPv6 in SQL
connection strings).

Also, make it optional.

Unused since egg bump from commit 80bfb5e0 .

It is not used in xwiki and lamp, does not work out of the box in erp5, and
prevents erp5 from moving further toward IPv6 support.
Do not drop its component SR and recipe just yet, as it might find some
use in the near future.

This reverts commit e9b76a68.
When kumo is built with IPv6 support, it stops supporting IPv4, which
breaks existing SRs.

Based on work by Romain Courteaud <romain@nexedi.com>.

Made possible with Nexedi's buildout, which de-serialises python types
transparently.