rabbit_channel: Restore start_link/11 for backward compatibility

start_link/11 calls start_link/12 with AmqpParams set to `undefined`.
This is what rabbit_channel_sup was doing as well as
rabbit_ct_broker_helpers in rabbitmq-ct-helpers.

Those modules use the restored start_link/11 again so the default value
of AmqpParams is stored in one place only.

(cherry picked from commit ce44331)

Author: dumbbell

src/rabbit_channel.erl

@@ -55,7 +55,7 @@
 
 -behaviour(gen_server2).
 
--export([start_link/12, do/2, do/3, do_flow/3, flush/1, shutdown/1]).
+-export([start_link/11, start_link/12, do/2, do/3, do_flow/3, flush/1, shutdown/1]).
 -export([send_command/2, deliver/4, deliver_reply/2,
          send_credit_reply/2, send_drained/2]).
 -export([list/0, info_keys/0, info/1, info/2, info_all/0, info_all/1,
@@ -237,6 +237,17 @@
 
 %%----------------------------------------------------------------------------
 
+-spec start_link
+        (channel_number(), pid(), pid(), pid(), string(), rabbit_types:protocol(),
+         rabbit_types:user(), rabbit_types:vhost(), rabbit_framing:amqp_table(),
+         pid(), pid()) ->
+            rabbit_types:ok_pid_or_error().
+
+start_link(Channel, ReaderPid, WriterPid, ConnPid, ConnName, Protocol, User,
+           VHost, Capabilities, CollectorPid, Limiter) ->
+    start_link(Channel, ReaderPid, WriterPid, ConnPid, ConnName, Protocol, User,
+           VHost, Capabilities, CollectorPid, Limiter, undefined).
+
 -spec start_link
         (channel_number(), pid(), pid(), pid(), string(), rabbit_types:protocol(),
          rabbit_types:user(), rabbit_types:vhost(), rabbit_framing:amqp_table(),

src/rabbit_channel_sup.erl

@@ -66,7 +66,7 @@ start_link({tcp, Sock, Channel, FrameMax, ReaderPid, ConnName, Protocol, User,
           {channel, {rabbit_channel, start_link,
                      [Channel, ReaderPid, WriterPid, ReaderPid, ConnName,
                       Protocol, User, VHost, Capabilities, Collector,
-                      LimiterPid, undefined]},
+                      LimiterPid]},
            intrinsic, ?FAIR_WAIT, worker, [rabbit_channel]}),
     {ok, AState} = rabbit_command_assembler:init(Protocol),
     {ok, SupPid, {ChannelPid, AState}};