verify_callback not being called during WEBRick HTTPS test

[headius]

While working on jruby/jruby#6246 I found that the test_sni test in WEBrick's test_ssl.rb is failing because a verify_callback is not being called.

The assertion in question is here: https://github.com/ruby/webrick/blob/2c912ded39f2d3046203cde8b169dcf2c267017e/test/webrick/test_https.rb#L41

The callback is set just north of that line, and is intended to capture the subject. However since it never gets called, subject remains nil and the assertion fails.

[headius]

The test is easy to run:

$ ruby -Ilib -Itest/lib test/webrick/test_https.rb -n test_sni

And the error that results:

TestWEBrickHTTPS#test_sni [/Users/headius/projects/webrick/test/webrick/utils.rb:72]:
exceptions on 1 threads:
#<Thread:0x61f05988@/Users/headius/projects/webrick/test/webrick/utils.rb:65 dead>:
/Users/headius/projects/webrick/test/lib/minitest/unit.rb:201:in `assert': <"/CN=localhost"> expected but was
<nil>. (MiniTest::Assertion)
	from /Users/headius/projects/webrick/test/lib/test/unit/assertions.rb:37:in `assert'
	from /Users/headius/projects/webrick/test/lib/test/unit/assertions.rb:298:in `assert_equal'
	from test/webrick/test_https.rb:43:in `https_get'
	from test/webrick/test_https.rb:94:in `block in test_sni'
	from /Users/headius/projects/webrick/test/webrick/utils.rb:67:in `block in start_server'

Note that the assertion here must be commented out in order to see this failure, due to #201: https://github.com/ruby/webrick/blob/2c912ded39f2d3046203cde8b169dcf2c267017e/test/webrick/test_https.rb#L90