Resolve pernicious race between destructor and thread functions by insisting that destructor is invoked after the class has gone back to being a harmless single-threaded thing.

This reveals an issue that needs to be solved:
D0713 14:48:28.049861213   14503 server.c:704]               Waiting for 44 channels and 0/1 listeners to be destroyed before shutting down server

containers

a map to 2 vectors. Additional minor changes needed (e.g., override->GRPC_OVERRIDE,
nullptr->grpc::nullptr)

Implemented ability to sleep before sending response as intended
by the ResponseParameters proto.

This is for the same reasons as ParseJson, that is so that we can limit
the scope of the proto namespace differences between internal and
external.