tests: Update submodule to the latest commit on libcgroup-tests main branch

For future reference, here are the steps to do this:
	$ ./bootstrap.sh
	$ git submodule update  --remote tests
	$ git add tests

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>

diff --git a/tests b/tests
index 3d3364813b7b80f42aa74f0bec9de33efadf4200..7c998caddcd8236fe4191841e361b401697fb777 160000 (submodule)
--- a/tests
+++ b/tests
@@ -1 +1 @@
-Subproject commit 3d3364813b7b80f42aa74f0bec9de33efadf4200
+Subproject commit 7c998caddcd8236fe4191841e361b401697fb777