Follow-p to r1496127: Have the test try a date which is not only
unambiguous, but also is not exactly the svn:date propval.

* subversion/tests/cmdline/checkout_tests.py
  (datetime): Import.
  (checkout_peg_rev_date): Compute a date different than the svn:date value,
    document the reason, and remove a sleep() call which is now unneeded.

Patch by: danielsh
(I tested this with Python 2.5.6 works fine)


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1567492 13f79535-47bb-0310-9956-ffa450edef68