Create this issue to avoid involving too many things in a single PR.
Not end of the world since the inheritance is only used by test but no production. And tests are passing.
Repro steps:
#8485
#4863
source/server/server.cc:406:3: note: Taking false branch
if (bootstrap_.dynamic_resources().has_lds_config()) {
^
source/server/server.cc:418:46: note: Call to virtual function during construction
Runtime::LoaderSingleton::get().initialize(clusterManager());