asyncio: Fix BaseSelectorEventLoopTests (GH-4595) (#4599)

Currently, two tests fail with PYTHONASYNCIODEBUG=1 (or using -X
dev).
(cherry picked from commit 92f9339)

Author: miss-islington

Lib/test/test_asyncio/test_selector_events.py

@@ -188,6 +188,7 @@ def test_sock_recv_reconnection(self):
         sock = mock.Mock()
         sock.fileno.return_value = 10
         sock.recv.side_effect = BlockingIOError
+        sock.gettimeout.return_value = 0.0
 
         self.loop.add_reader = mock.Mock()
         self.loop.remove_reader = mock.Mock()
@@ -268,6 +269,7 @@ def test_sock_sendall_reconnection(self):
         sock = mock.Mock()
         sock.fileno.return_value = 10
         sock.send.side_effect = BlockingIOError
+        sock.gettimeout.return_value = 0.0
 
         self.loop.add_writer = mock.Mock()
         self.loop.remove_writer = mock.Mock()