Assert that the cluster has elected the correct leader out of all nodes in the cluster. First member in the cluster ring is expected leader. Note that this can only be used for a cluster with all members in Up status, i.e. use `awaitMembersUp` before using this method. The reason for that is that the cluster leader is preferably a member with status Up or Leaving and that information can't be determined from the `RoleName`.

public void AssertLeaderIn(
	ImmutableList<RoleName> nodesInCluster
)

member AssertLeaderIn : 
        nodesInCluster : ImmutableList<RoleName> -> unit