The neutron.common.topics module was rehomed into neutron-lib with
commit Ie88b84949cbd55a4e7ad06341aab77b286cdc485
This patch consumes it by removing the rehomed module from neutron
and using the module from neutron-lib instead.
NeutronLibImpact
Change-Id: Ia4a4604c259ce862597de80c6deeb3d408bf0e95