clear view path cache between tests

The cache for `render file:` seems to also be used in the case of
`render(string)`.  If one is supposed to be a hit and the other is
supposed to be a miss, and they both reference the same file, then the
cache could return incorrect values.  This commit clears the cache
between runs so that we get non-cached behavior.

actionpack/test/controller/render_test.rb

@@ -265,6 +265,11 @@ def accessing_logger_in_template
 class ExpiresInRenderTest < ActionController::TestCase
   tests TestController
 
+  def setup
+    super
+    ActionController::Base.view_paths.paths.each(&:clear_cache)
+  end
+
   def test_dynamic_render_with_file
     # This is extremely bad, but should be possible to do.
     assert File.exist?(File.join(File.dirname(__FILE__), '../../test/abstract_unit.rb'))