Use /var/lib/lava-* for tests files on Ubuntu

Some Ubuntu-derived distros such as Apertis have a read-only root file
system, and it can't be re-mounted as rw.  So to be able to store LAVA
test files, move the directories to /var/lib/ instead as this has
write permissions.
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>

lava_dispatcher/deployment_data.py

@@ -198,9 +198,9 @@ ubuntu = {
     "distro": "ubuntu",
     "tar_flags": "--warning no-timestamp",
     "lava_test_sh_cmd": "/bin/sh",
-    "lava_test_dir": "/lava-%s",
+    'lava_test_dir': '/var/lib/lava-%s',
     "lava_test_results_part_attr": "root_part",
-    "lava_test_results_dir": "/lava-%s",
+    'lava_test_results_dir': '/var/lib/lava-%s',
     "lava_test_shell_file": "~/.bashrc",
 }