fix os:system_time/1 time unit in credit_flow trace events, which is crashing

messaging components which use flow control when calling credit_flow:block/1,
credit_flow:unblock/1 and/or via credit_flow:peer_down/1 and handle_bump_msg/1.
This can crash all messaging components (connections, channels, queues, msg-store)
when trace is enabled and flow is set or cleared (amqp-1.0 included).

Author: Ayanda-D

deps/rabbit_common/src/credit_flow.erl

@@ -99,13 +99,13 @@
                                       {from_info, erlang:process_info(FROM)},
                                       {timestamp,
                                        os:system_time(
-                                         milliseconds)}])).
+                                         millisecond)}])).
 -define(TRACE_UNBLOCKED(SELF, FROM), rabbit_event:notify(credit_flow_unblocked,
                                        [{process, SELF},
                                         {from, FROM},
                                         {timestamp,
                                          os:system_time(
-                                           milliseconds)}])).
+                                           millisecond)}])).
 -else.
 -define(TRACE_BLOCKED(SELF, FROM), ok).
 -define(TRACE_UNBLOCKED(SELF, FROM), ok).