test_thread.rb: let main thread exit from Thread.new

* test/ruby/test_thread.rb (test_main_thread_status_at_exit): let
  the main thread run to ensure exiting from Thread.new.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47224 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_thread.rb

@@ -820,6 +820,7 @@ _eom
     assert_in_out_err([], <<-'INPUT', ["false false aborting"], [])
 Thread.new(Thread.current) {|mth|
   begin
+    mth.run
     Thead.pass until mth.stop?
     p :mth_stopped # don't run if killed by rb_thread_terminate_all
   ensure