CLI: Fix match of discover peers command test

This previously emitted a warning because Elixir will rebind `this_node`
by default, so the `this_node` binding in the line above was unused.
(As opposed to Erlang which would treat this as a match - rejecting
the binding if `this_node` was not equal to the value being matched.)
The node needed to be adjusted as well - `node()` returned the ExUnit
runner's node while the command returned the remote node, which is
stored in the context under `opts.node`.

Author: the-mikedavis

deps/rabbitmq_cli/test/diagnostics/discover_peers_command_test.exs

@@ -37,7 +37,7 @@ defmodule DiscoverPeersCommandTest do
 
   @tag test_timeout: 15000
   test "run: returns a list of nodes when the backend isn't configured", context do
-    this_node = node()
-    assert match?({:ok, {[this_node], _}}, @command.run([], context[:opts]))
+    this_node = context.opts.node
+    assert match?({:ok, {[^this_node], _}}, @command.run([], context[:opts]))
   end
 end