Revert "Revert "Ensure that exit code 0 is used for "stop" command""

This reverts commit 547be43.

The change in 1518b60 is in line with the expected
stop behavior in 3.6.x.

For 3.7.0 we are still contemplating what it should be.

Author: michaelklishin

src/rabbit_cli.erl

@@ -122,15 +122,12 @@ main(ParseFun, DoFun, UsageMod) ->
                 _ ->
                     print_error("unable to connect to node ~w: ~w", [Node, Reason]),
                     print_badrpc_diagnostics([Node]),
-                    case Command of
-                        stop -> rabbit_misc:quit(?EX_OK);
-                        _    -> rabbit_misc:quit(?EX_UNAVAILABLE)
-                    end
+                    exit_badrpc(Command)
             end;
         {badrpc_multi, Reason, Nodes} ->
             print_error("unable to connect to nodes ~p: ~w", [Nodes, Reason]),
             print_badrpc_diagnostics(Nodes),
-            rabbit_misc:quit(?EX_UNAVAILABLE);
+            exit_badrpc(Command);
         function_clause ->
             print_error("operation ~w used with invalid parameter: ~p",
                         [Command, Args]),
@@ -143,6 +140,11 @@ main(ParseFun, DoFun, UsageMod) ->
             rabbit_misc:quit(?EX_SOFTWARE)
     end.
 
+exit_badrpc(stop) ->
+    rabbit_misc:quit(?EX_OK);
+exit_badrpc(_) ->
+    rabbit_misc:quit(?EX_UNAVAILABLE).
+
 start_distribution_anon(0, LastError) ->
     {error, LastError};
 start_distribution_anon(TriesLeft, _) ->