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

test/ruby/test_continuation.rb

@@ -37,9 +37,11 @@ class TestContinuation < Test::Unit::TestCase
 
   def test_error
     cont = callcc{|c| c}
-    assert_raise(RuntimeError){
-      Thread.new{cont.call}.join
-    }
+    Thread.new{
+      assert_raise(RuntimeError){
+        cont.call
+      }
+    }.join
     assert_raise(LocalJumpError){
       callcc
     }
@@ -132,4 +134,3 @@ class TestContinuation < Test::Unit::TestCase
     assert_equal 3, @memo
   end
 end
-