test: Use larger time values in testing_test
test: Use larger time values in testing_test

This test was flaky on appveyor. Also expand comments about what
exactly the test is doing.

dongpinglai/my_tornado,mivade/tornado,tornadoweb/tornado,lilydjwg/tornado,mivade/tornado,dongpinglai/my_tornado,mivade/tornado,dongpinglai/my_tornado,tornadoweb/tornado,lilydjwg/tornado,mivade/tornado,dongpinglai/my_tornado,dongpinglai/my_tornado,dongpinglai/my_tornado,lilydjwg/tornado,tornadoweb/tornado,lilydjwg/tornado,tornadoweb/tornado,mivade/tornado