selftests/unit/test_runner_queue.py: use absolute path for module

Looks like the Python 3 module import code behaves differently than
Python 2 with regards to where it looks modules by name:

   File "/home/cleber/src/avocado/avocado/avocado/core/test.py", line 932, in _run_avocado
      raise test_exception
   File "/home/cleber/src/avocado/avocado/avocado/core/test.py", line 819, in _run_avocado
      testMethod()
   File "/home/cleber/src/avocado/avocado/avocado/core/test.py", line 1371, in test
      self.error(self.exception)
   File "/home/cleber/src/avocado/avocado/avocado/core/test.py", line 1041, in error
      raise exceptions.TestError(message)\navocado.core.exceptions.TestError: Traceback (most recent call last):
   File "/usr/lib64/python3.6/imp.py", line 297, in find_module
      raise ImportError(_ERR_MSG.format(name), name=name)
   ImportError: No module named \'whiteboard\'\n\n'

Effectively, this means when running this test, on Python 3, on the
parallel mode, the change of directory implemented there
(on selftests/checkall) will make Python 3 fail to find this module,
and the test will fail.

This makes the reference to the module path absolute, so no matter
where this test is run from, it should be able to find the module.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

selftests/unit/test_runner_queue.py

@@ -4,6 +4,7 @@ import tempfile
 import unittest
 import multiprocessing
 import multiprocessing.queues
+import os
 
 from avocado.core.job import Job
 from avocado.core.result import Result
@@ -42,12 +43,15 @@ class TestRunnerQueue(unittest.TestCase):
         """
         Tests if the whiteboard content is the expected one
         """
+        this = os.path.abspath(__file__)
+        base = os.path.dirname(os.path.dirname(os.path.dirname(this)))
+        module = os.path.join(base, 'examples', 'tests', 'whiteboard.py')
         factory = ['WhiteBoard',
                    {'methodName': 'test',
                     'tags': set([]),
                     'params': ([TreeNode(name='')], ['/run/*']),
                     'job': self.job,
-                    'modulePath': 'examples/tests/whiteboard.py',
+                    'modulePath': module,
                     'base_logdir': self.tmpdir}]
         msg = self._run_test(factory)