logilab-common #63998 pyro_ext: allow to create a server without registering with a pyro ns [validation pending]

used by https://www.cubicweb.org/ticket/1528533

prioritynormal
typeenhancement
done in0.55.2
load0.300
load left0.000
closed by#872d09e4ee4f allow to create a pyro server without registering it to a pyro ns (closes #63998)