Refactor get_logs()

Sometimes, 'tar' returns exit code 1, because some files in the
/var/log/ were changed during the archiving.

To avoid this error, let's copy /var/log/ to another place first.

Other changes:

- extend the collected information from the nodes
(inspired by the fuel snapshots from Nailgun)

- allow get_logs() to execute also when rep_setup.failed is set
  (when any fixture failed)

Change-Id: I59caeb9df42639df53d439866c26bac8ba59e696
diff --git a/tcp_tests/fixtures/salt_fixtures.py b/tcp_tests/fixtures/salt_fixtures.py
index 58c8509..9bd24b3 100644
--- a/tcp_tests/fixtures/salt_fixtures.py
+++ b/tcp_tests/fixtures/salt_fixtures.py
@@ -35,7 +35,7 @@
 @pytest.mark.revert_snapshot(ext.SNAPSHOT.salt_deployed)
 @pytest.fixture(scope='function')
 def salt_deployed(revert_snapshot, request, config,
-                  hardware, underlay, salt_actions, grab_versions, snapshot):
+                  hardware, underlay, salt_actions, snapshot, grab_versions):
     """Fixture to get or install salt service on environment
 
     :param revert_snapshot: fixture that reverts snapshot that is specified