Running cephcsi in docker swarm currently requires serving both
the nodeserver and controllerserver over the same socket.
This leads to errors like
> FATAL: [core] grpc: Server.RegisterService found duplicate
> service registration for \"fence.FenceController\""
...since `FenceController` is registererd once per server type.
Commit proposes simple fix by registering `FenceController` only once
when at least one of `IsControllerServer` or `IsNodeServer` is `true`.
Signed-off-by: monoamin <precision1998@gmail.com>
71decb822d