Change rabbit_nodes:all_running/0 behaviour.

Make it return only nodes which are fully started
instead of what mnesia thinks is started.
In all places we use them, we assume they should
be started.

[#154569776]

Author: hairyhum

src/rabbit_nodes.erl

@@ -85,4 +85,5 @@ set_cluster_name(Name, Username) ->
 ensure_epmd() ->
     rabbit_nodes_common:ensure_epmd().
 
-all_running() -> rabbit_mnesia:cluster_nodes(running).
+all_running() -> [ Node || Node <- rabbit_mnesia:cluster_nodes(running),
+                           is_running(Node, rabbit) ].