Fix race condition in Logger.ErrorHandlerTest

When crashing the error logger handler, the handler's watcher could log
its message before Logger was flushed, causing the watcher's log
message to appear in the first, rather than second, capture_log.

Author: fishcakez

lib/logger/test/logger/error_handler_test.exs

@@ -2,8 +2,8 @@ defmodule Logger.ErrorHandlerTest do
   use Logger.Case
 
   test "survives after crashes" do
-    assert error_log(:info_msg, "~p~n", []) == ""
     assert capture_log(fn ->
+      :error_logger.info_msg("~p~n", [])
       wait_for_handler(:error_logger, Logger.ErrorHandler)
     end) =~ "[error] GenEvent handler Logger.ErrorHandler installed at :error_logger\n" <>
             "** (exit) an exception was raised:"