run-report: Allow tests to spawn and control their own sessiond

The run-report script can spawn a sessiond if the 'daemon' key value is
set to 'True' in the test description dictionary. If the 'daemon' key is
set to 'False', the TEST_NO_SESSIOND environment variable is set so no
sessiond can be spawned in the tests. This variable is also set when the
run-report spawn its own sessiond.

This behavior has the unfortunate side-effect of restricting any kind of
spawning and control of the sessiond via the tests.

Fix this issue by allowing the tests to spawn their own sessiond. We
need to pass an additional env dictionary to the TestWorker in order to
spawn the test with the proper environment variables set.

To indicate that a test will spawn and manage its own sessiond, the
'daemon' key value should be set to the "test" string.

Signed-off-by: Christian Babeux <christian.babeux@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>