Fix test-all tests to avoid creating report_on_exception warnings

* The warnings are shown by Thread.report_on_exception defaulting to
  true. [Feature #14143] [ruby-core:83979]
* Improves tests by narrowing down the scope where an exception
  is expected.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61188 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
[ky: this effectively reverts commit 01445af ("test/test_ssl:
 prevent changing default internal encoding", 2017-11-26). This is OK
 since EnvUtil.with_default_internal has been made thread-safe.]
Sync-with-trunk: r61188

Author: eregon

test/test_ssl.rb

@@ -1259,13 +1259,15 @@ def test_fallback_scsv
       ctx2.enable_fallback_scsv
       ctx2.max_version = OpenSSL::SSL::TLS1_1_VERSION
       s2 = OpenSSL::SSL::SSLSocket.new(sock2, ctx2)
-      t = Thread.new { s2.connect }
-      assert_raise_with_message(OpenSSL::SSL::SSLError, /inappropriate fallback/) {
-        s1.accept
+      t = Thread.new {
+        assert_raise_with_message(OpenSSL::SSL::SSLError, /inappropriate fallback/) {
+          s2.connect
+        }
       }
       assert_raise_with_message(OpenSSL::SSL::SSLError, /inappropriate fallback/) {
-        t.join
+        s1.accept
       }
+      t.join
     ensure
       sock1.close
       sock2.close