Job main loop: functional tests timing

Looks like test bots, such as travis, can have very little resources
at times and run things really slowly, example:

```
======================================================================
FAIL: Sleeptest is supposed to take 1 second, let's make a sandwich of
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/avocado-framework/avocado/selftests/all/
functional/avocado/basic_tests.py", line 238, in test_runner_sleep_fail_sleep_timing
    self.assertLess(actual_time, 4.0)
AssertionError: 4.036144018173218 not less than 4.0
```

Let's increase the maximum expected times.

Signed-off-by: Cleber Rosa <crosa@redhat.com>