Make the rexi:stream2 interface unacked message limit configurable (#2360)

Also lower the default stream_limit to 5 based on the results of
performance testing.

Co-authored-by: Adam Kocoloski <kocolosk@apache.org>
Co-authored-by: Kyle Snavely <kjsnavely@gmail.com>
diff --git a/rel/overlay/etc/default.ini b/rel/overlay/etc/default.ini
index f5f0578..669977e 100644
--- a/rel/overlay/etc/default.ini
+++ b/rel/overlay/etc/default.ini
@@ -214,6 +214,7 @@
 ; [rexi]
 ; buffer_count = 2000
 ; server_per_node = true
+; stream_limit = 5
 
 ; [global_changes]
 ; max_event_delay = 25
diff --git a/src/rexi/src/rexi.erl b/src/rexi/src/rexi.erl
index ead5bee..170503b 100644
--- a/src/rexi/src/rexi.erl
+++ b/src/rexi/src/rexi.erl
@@ -211,9 +211,10 @@
         exit(timeout)
     end.
 
-%% @equiv stream2(Msg, 10, 300000)
+%% @equiv stream2(Msg, 5, 300000)
 stream2(Msg) ->
-    stream2(Msg, 10, 300000).
+    Limit = config:get_integer("rexi", "stream_limit", 5),
+    stream2(Msg, Limit).
 
 %% @equiv stream2(Msg, Limit, 300000)
 stream2(Msg, Limit) ->