Add upgrade test for Riak Control

Some issues have been found when running a mixed cluster with Riak
Control enabled.  This tests the typical upgrade scenario of a
customer and verifies that Riak Control at least doesn't crash any of
the nodes while in a mixed cluster state.

See https://github.com/basho/riak_control/pull/120

tests/riak_control_upgrade.erl

@@ -0,0 +1,69 @@
+-module(riak_control_upgrade).
+-behavior(riak_test).
+-export([confirm/0]).
+-include_lib("eunit/include/eunit.hrl").
+-define(RC_ENABLE_CFG,
+        [{riak_core,
+          [
+           {https, [{"127.0.0.1", 8069}]},
+           {ssl,
+            [{certfile, "./etc/cert.pem"},
+             {keyfile, "./etc/key.pem"}
+            ]}
+          ]
+         },
+         {riak_control,
+          [
+           {enabled, true},
+           {auth, none}
+          ]
+         }
+        ]).
+
+%% TODO: verify everything is asserted
+
+%% NOTE: Assumes config contains both `legacy' and `previous' settings.
+confirm() ->
+    verify_upgrade(legacy, host_rc_on_old),
+    verify_upgrade(legacy, host_rc_on_new),
+    verify_upgrade(previous, host_rc_on_old),
+    verify_upgrade(previous, host_rc_on_new),
+    pass.
+
+%% Verify an upgrade from the `FromVsn' version.  This assumes there
+%% are `legacy' and `previous' keys in your `~/.riak_test.config'.
+%% The `HostRCOn' parameter determines whether Riak Control is hosted
+%% on the old or new version.
+verify_upgrade(FromVsn, HostRCOn) ->
+    lager:info("Verify upgrade ~p ~p", [FromVsn, HostRCOn]),
+    Nodes = rt:build_cluster([{legacy, ?RC_ENABLE_CFG}|lists:duplicate(2, legacy)]),
+    verify_alive(Nodes),
+    UpgradeSeq = upgrade_seq(Nodes, HostRCOn),
+    [upgrade_and_verify_alive(Nodes, ToUpgrade) || ToUpgrade <- UpgradeSeq],
+    rt:setup_harness(ignored, ignored).
+
+verify_alive(Nodes) ->
+    lager:info("Verify nodes ~p are alive", [Nodes]),
+    [rt:wait_for_service(Node, riak_kv) || Node <- Nodes].
+
+upgrade_and_verify_alive(Nodes, ToUpgrade) ->
+    upgrade(ToUpgrade, current),
+    verify_alive(Nodes).
+
+%% Determine the upgrade sequence for `Nodes' based on `HostRCOn'.
+%% This function assumes that the first node in `Nodes' is the RC
+%% host.
+upgrade_seq(Nodes, host_rc_on_old) ->
+    %% Upgrade the RC host last because you want an old RC version to
+    %% talk to new nodes.
+    lists:reverse(Nodes);
+upgrade_seq(Nodes, host_rc_on_new) ->
+    %% Upgrade RC host first because you want new RC version to talk
+    %% to old nodes.
+    Nodes.
+
+upgrade(Node, Vsn) ->
+    lager:info("Upgrading ~p to ~p", [Node, Vsn]),
+    rt:upgrade(Node, Vsn),
+    rt:wait_for_service(Node, riak_kv),
+    ok.