Fix tests_stubs tests

Minor fixes for api changes from a while ago.
Since the "tests_stubs" directory starts with "tests_", it isn't/wasn't
run automatically by nosetests when the code was changed.
Add "enable_retries" to run_queue()
Make sure to increment the eta

We are ignoring the eta, but when app engine postpones a task for
a retry, it verifies the eta has increased.
More comprehensive test for retries

Ensure the retry parameter is tracked separately for tasks.
No new failures, but this better verifies that retries with the
queue runner are working.
Fix bool docstrings
Readd param description to docstrings
Add param docstrings for the two new functions
Merge pull request #124 from ericolson-wf/add_retries_to_test_runner

Add retries to test runner