[open3] only close streams if a block is passed

Ref: 5429deb075beb9a2b67adae269bbac16325876d1

The previous change totally borke `popen2e` in this usage:

```ruby
require 'open3'
stdin, stdout, process = Open3.popen2e("cat")
puts stdout.read
```

1 files changed, 11 insertions, 0 deletions

diff --git a/test/test_open3.rb b/test/test_open3.rb
index 24bd08e597..47d471c031 100644
--- a/test/test_open3.rb
+++ b/test/test_open3.rb
@@ -149,6 +149,17 @@ class TestOpen3 < Test::Unit::TestCase
     }
   end
 
+  def test_popen2e_noblock
+    i, o, t = Open3.popen2e(RUBY, '-e', 'STDOUT.print STDIN.read')
+    i.print "baz"
+    i.close
+    assert_equal("baz", o.read)
+  ensure
+    i.close
+    o.close
+    t.join
+  end
+
   def test_capture3
     o, e, s = Open3.capture3(RUBY, '-e', 'i=STDIN.read; print i+"o"; STDOUT.flush; STDERR.print i+"e"', :stdin_data=>"i")
     assert_equal("io", o)