timing-dependent failures in test_adapter.txt

test_adapter.txt assumes that a request will take 0 ms to complete, and if it takes longer, it fails:

File "lib/lp/services/webapp/doc/test_adapter.txt", line 340, in test_adapter.txt
Failed example:
    get_request_statements()
Differences (ndiff with -expected +actual):
    - [(0, 0, 'SQL-main-master', 'SELECT 2', ...)]
    + [(0, 1, 'SQL-main-master', 'SELECT 2', ' File "bin/test", line 278, in <m
odule>\n testrunner.run([])\n File "/home/abentley/launchpad/stable/eggs/zop
e.testing-3.9.4_p4-py2.6.egg/zope/testing/testrunner/__init__.py", line 32, in run\n failed = run_internal(defaults, args, script_parts=script_parts)\n File "/home/abentley/launchpad/stable/eggs/zope.testing-3.9.4_p4-py2.6.egg/zope/testing/testrunner/__init__.py", line 45, in run_internal\n runner.run()\n File "/home/abentley/launchpad/stable/eggs/zope.testing-3.9.4_p4-py2.6.egg/zope/testi