tests: use never instead of dont_allow (#4671)

Backported from a2b935a.

---

If it use the object applied dont_allow in the other test through ObjectSpace.each_object, it will cause the error.
To relax object constraints, this patch will use never instead.

Signed-off-by: Shizuo Fujita <[email protected]>

test/plugin/out_forward/test_socket_cache.rb

@@ -17,7 +17,7 @@ class SocketCacheTest < Test::Unit::TestCase
       assert_equal(socket, c.checkout_or('key') { socket })
       c.checkin(socket)
 
-      sock = dont_allow(mock!).open
+      sock = mock!.open.never.subject
       assert_equal(socket, c.checkout_or('key') { sock.open })
     end
 
@@ -130,7 +130,7 @@ def teardown
 
       c = Fluent::Plugin::ForwardOutput::SocketCache.new(10, $log)
       sock = mock!.close { 'closed' }.subject
-      sock2 = dont_allow(mock!).close
+      sock2 = mock!.close.never.subject
       stub(sock).inspect
       stub(sock2).inspect
 
@@ -154,7 +154,7 @@ def teardown
       Timecop.freeze(Time.parse('2016-04-13 14:00:00 +0900'))
 
       c = Fluent::Plugin::ForwardOutput::SocketCache.new(10, $log)
-      sock = dont_allow(mock!).close
+      sock = mock!.close.never.subject
       stub(sock).inspect
       c.checkout_or('key') { sock }
 

test/test_event_router.rb

@@ -175,7 +175,7 @@ def event_router
       test "don't call default collector when tag matched" do
         event_router.add_rule('test', output)
         assert_rr do
-          dont_allow(default_collector).emit_events('test', is_a(OneEventStream))
+          mock(default_collector).emit_events('test', is_a(OneEventStream)).never
           event_router.emit('test', Engine.now, 'k' => 'v')
         end
         # check emit handler doesn't catch rr error
@@ -201,7 +201,7 @@ def filter_stream(_tag, es); end
         event_router.add_rule('test', filter)
 
         assert_rr do
-          dont_allow(filter).filter_stream('test', is_a(OneEventStream)) { events }
+          mock(filter).filter_stream('test', is_a(OneEventStream)).never
           event_router.emit('foo', Engine.now, 'k' => 'v')
         end
       end