fix failure in test_global_pinger_memo

Testing Done:
test_global_pinger_memo tries to confirm that pinger times out when the cache takes to long to respond. When the timeout value and the time the cache takes to respond are too close, the test fails.

I increased difference between the cache response time and the timeout value by .01 seconds.

CI is running: https://travis-ci.org/pantsbuild/pants/builds/86543563

Reviewed at https://rbcommons.com/s/twitter/r/3007/

tests/python/pants_test/cache/test_pinger.py

@@ -60,7 +60,7 @@ def test_pinger_timeout_config(self):
     self.assertEqual(ping_results[self.slow_netloc], Pinger.UNREACHABLE)
 
   def test_global_pinger_memo(self):
-    fast_pinger = Pinger(timeout=self.slow_seconds, tries=2)
+    fast_pinger = Pinger(timeout=self.slow_seconds - .01, tries=2)
     slow_pinger = Pinger(timeout=self.timeout_seconds, tries=2)
     self.assertEqual(fast_pinger.pings([self.slow_netloc])[0][1], Pinger.UNREACHABLE)
     self.assertNotEqual(slow_pinger.pings([self.slow_netloc])[0][1], Pinger.UNREACHABLE)