skip on other threads.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59151 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_settracefunc.rb

@@ -1605,6 +1605,7 @@ class TestSetTraceFunc < Test::Unit::TestCase
   def tp_return_value mid
     ary = []
     TracePoint.new(:return, :b_return){|tp| ary << [tp.event, tp.method_id, tp.return_value]}.enable{
+      next if !target_thread?
       send mid
     }
     ary.pop # last b_return event is not required.