Support Configuration with Resolver, Master, and Proxy always on the same host

With clients and transaction logs distributed across multiple hosts, the only way to guarantee at most 2 network round trips in the synchronous commit path is to run all of the master, resolver, and proxy roles on the same host. However, if this host dies, the current role recruitment may recruit these roles on different hosts. To guarantee low commit latency at all times, it would be nice to have a knob to guarantee that all master, proxy, and resolver roles are recruited on a single host with each recovery.