component/userhosts: use github.com/figiel/hosts to workaround recent libc

In ubuntu 21.04 (libc6 2.33-0ubuntu5) or current debian testing
(libc6 2.32-5) no longer use open to open /etc/hosts, but what appears
as "openat" in strace output - but can not be injected by

This uses https://github.com/figiel/hosts which uses another approach
of overloading getaddrinfo, gethostbyname* and inet_aton. This does not
original version of libuserhosts, but a version slightly modified to
behave the same way as nexedi's userhosts.

component/userhosts/buildout.cfg

 [userhosts]
 recipe = slapos.recipe.cmmi
 shared = true
-url = https://lab.nexedi.com/nexedi/userhosts/repository/${:revision}/archive.tar.gz
-revision = a05fe5a3a5cb7005351ef4ec41460089f3ce4d0a
-md5sum = 5a80b4d962d975f290a60cf790c3334d
+url = https://github.com/perrinjerome/hosts/archive/${:revision}.tar.gz
+revision = 7bd71dd0bf969f4e76928f7fedf2e87a3e7f6375
+md5sum = d150eb5dc464070dc5023b0f575a3386
 configure-command = true
 make-options = PREFIX=@@LOCATION@@
-make-targets = check install
+make-targets = test install