Reuse timestamp in rabbit_message_interceptor

 ## What?
`mc:init()` already sets mc annotation `rts` (received timestamp).
This commit reuses this timestamp in `rabbit_message_interceptor`.

 ## Why?
`os:system_time/1` can jump forward or backward between invocations.
Using two different timestamps for the same meaning, the time the message
was received by RabbitMQ, can be misleading.

(cherry picked from commit f447986)

Author: ansd

deps/rabbit/src/rabbit_message_interceptor.erl

@@ -27,9 +27,9 @@ intercept(Msg, set_header_routing_node, Overwrite) ->
     Node = atom_to_binary(node()),
     set_annotation(Msg, ?HEADER_ROUTING_NODE, Node, Overwrite);
 intercept(Msg0, set_header_timestamp, Overwrite) ->
-    Millis = os:system_time(millisecond),
-    Msg = set_annotation(Msg0, ?HEADER_TIMESTAMP, Millis, Overwrite),
-    set_timestamp(Msg, Millis, Overwrite).
+    Ts = mc:get_annotation(?ANN_RECEIVED_AT_TIMESTAMP, Msg0),
+    Msg = set_annotation(Msg0, ?HEADER_TIMESTAMP, Ts, Overwrite),
+    set_timestamp(Msg, Ts, Overwrite).
 
 -spec set_annotation(mc:state(), mc:ann_key(), mc:ann_value(), boolean()) -> mc:state().
 set_annotation(Msg, Key, Value, Overwrite) ->