Let's run action pack tests with Dalli

There is no memcache gem left in repo.

actionpack/test/dispatch/session/mem_cache_store_test.rb

@@ -34,9 +34,9 @@ def call_reset_session
   end
 
   begin
-    require 'memcache'
-    memcache = MemCache.new('localhost:11211')
-    memcache.set('ping', '')
+    require 'dalli'
+    ss = Dalli::Client.new('localhost:11211').stats
+    raise Dalli::DalliError unless ss['localhost:11211']
 
     def test_setting_and_getting_session_value
       with_test_route_set do
@@ -165,7 +165,7 @@ def test_prevents_session_fixation
         assert_not_equal session_id, cookies['_session_id']
       end
     end
-  rescue LoadError, RuntimeError
+  rescue LoadError, RuntimeError, Dalli::DalliError
     $stderr.puts "Skipping MemCacheStoreTest tests. Start memcached and try again."
   end