test: adjust list-sessions for systemd 256 changes

In systemd 256 list-session now also includes a manager session:

4 1000 admin -    538    user          web console no   -
5 1000 admin -    544    manager       -           no   -

test/verify/check-session

@@ -50,7 +50,8 @@ class TestSession(testlib.MachineCase):
 
         # Check session type
         if not m.ostree_image:
-            session_id = m.execute("loginctl list-sessions | awk '/admin/ {print $1}'").strip()
+            # Systemd 256 also shows a class=manager session for admin
+            session_id = m.execute("loginctl list-sessions | grep -v manager | awk '/admin/ {print $1}'").strip()
             self.assertEqual(m.execute(f"loginctl show-session -p Type {session_id}").strip(), "Type=web")
 
         # Logout

test/verify/check-static-login

@@ -830,6 +830,9 @@ matchrule = <SUBJECT>^DC=LAN,DC=COCKPIT,CN=alice$
                 self.assertGreaterEqual(len(sessions), 1)
                 for session in sessions:
                     out = m.execute('loginctl session-status ' + session)
+                    # Skip manager session
+                    if "Class: manager" in out:
+                        continue
                     if "State: active" in out:  # skip closing sessions
                         self.assertIn(session_leader, out)
                         self.assertIn('cockpit-bridge', out)